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1 NAME______________________________ IB PHYSICS HL REVIEW PACKET: MEASUREMENT, DATA, & GRAPHING 1. Data based question. This question is about change of electrical resistance with temperature. The table below gives values of the resistance R of an electrical component for different values of its temperature T. (Uncertainties in measurement are not shown.) T/°C 1.2 2.0 3.5 5.2 6.8 8.1 9.6 R/3590 3480 3250 3060 2880 2770 2650 (a) On the grid below, plot a graph to show the variation with temperature T of the resistance R. Show values on the temperature axis from T = 0°C to T = 10°C. (3) (b) (i) Draw a curve that best fits the points you have plotted. Extend your curve to cover the temperature range from 0°C to 10°C. (1) (ii) Use your graph to determine the resistance at 0°C and at 10°C. Resistance at 0°C = ...............................................Resistance at 10°C = .............................................(2) (c) On your graph, draw a straight-line between the resistance values at 0°C and at 10°C. This line shows the variation with temperature (between 0°C and 10°C) of the resistance, assuming a linear change. (1) (d) (i) Assuming a linear change of resistance with temperature, use your graph to determine the temperature at which the resistance is 3060 . Temperature = .........................................................°C (1) (ii) Use your answer in (d)(i) to calculate the percentage difference in the temperature for a resistance of 3060 that results from assuming a linear change rather than the non-linear change. ........................................................................................................................... ........................................................................................................................... (3)
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Page 1: IB Physics Review-Measurement - Wikispaceswsscience.wikispaces.com/file/view/IB+Physics+Review-Measureme… · IB PHYSICS HL REVIEW PACKET: ... (4) (b) Draw the line of ... In the

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NAME______________________________

IB PHYSICS HL

REVIEW PACKET: MEASUREMENT, DATA, & GRAPHING

1. Data based question. This question is about change of electrical resistance with temperature.

The table below gives values of the resistance R of an electrical component for different values of its temperature T. (Uncertainties in measurement are not shown.)

T/°C 1.2 2.0 3.5 5.2 6.8 8.1 9.6

R/Ω 3590 3480 3250 3060 2880 2770 2650

(a) On the grid below, plot a graph to show the variation with temperature T of the resistance R. Show values on the temperature axis from T = 0°C to T = 10°C.

(3)

(b) (i) Draw a curve that best fits the points you have plotted. Extend your curve to cover the temperature range from 0°C to 10°C.

(1)

(ii) Use your graph to determine the resistance at 0°C and at 10°C.

Resistance at 0°C = ...............................................Ω

Resistance at 10°C = .............................................Ω (2)

(c) On your graph, draw a straight-line between the resistance values at 0°C and at 10°C. This line shows the variation with temperature (between 0°C and 10°C) of the resistance, assuming a linear change.

(1)

(d) (i) Assuming a linear change of resistance with temperature, use your graph to determine the temperature at which the resistance is 3060 Ω.

Temperature = .........................................................°C (1)

(ii) Use your answer in (d)(i) to calculate the percentage difference in the temperature for a resistance of 3060 Ω that results from assuming a linear change rather than the non-linear change.

...........................................................................................................................

........................................................................................................................... (3)

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2. This question is about an experiment designed to investigate Newton’s second law.

In order to investigate Newton’s second law, David arranged for a heavy trolley to be accelerated by small weights, as shown below. The acceleration of the trolley was recorded electronically. David recorded the acceleration for different weights up to a maximum of 3.0 N. He plotted a graph of his results.

heavy trolleyacceleration

pulley

weight

(a) Describe the graph that would be expected if two quantities are proportional to one another.

.....................................................................................................................................

..................................................................................................................................... (2)

(b) David’s data are shown below, with uncertainty limits included for the value of the weights. Draw the best-fit line for these data.

1.40

1.20

1.00

0.80

0.60

0.40

0.20

0.000.00 0.50 1.00 1.50 2.00 2.50

weight / N

acceleration/ ms–2

(2)

(c) Use the graph to

(i) explain what is meant by a systematic error.

...........................................................................................................................

........................................................................................................................... (2)

(ii) estimate the value of the frictional force that is acting on the trolley.

........................................................................................................................... (1)

(iii) estimate the mass of the trolley.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2

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3. This question is about measuring the permittivity of free space ε0.

The diagram below shows two parallel conducting plates connected to a variable voltage supply. The plates are of equal areas and are a distance d apart.

Vdvariable voltage supply

+

The charge Q on one of the plates is measured for different values of the potential difference V applied between the plates. The values obtained are shown in the table below. Uncertainties in the data are not included.

V / V Q / nC

10.0 30

20.0 80

30.0 100

40.0 160

50.0 180

(a) Plot a graph of V (x-axis) against Q (y-axis).

(4)

(b) Draw the line of best fit for the data points. (1)

(c) Determine the gradient of your best-fit line. (2)

.....................................................................................................................................

.....................................................................................................................................

(d) The gradient of the graph is a property of the two plates and is known as capacitance. Deduce the units of capacitance.

..................................................................................................................................... (1)

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The relationship between Q and V for this arrangement is given by the expression

Q = Vd

A0ε

where A is the area of one of the plates.

In this particular experiment A = 0.20 m2 and d = 0.50 mm.

(e) Use your answer to (c) to determine a value for ε0.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 11 marks)

4. This question is about power output of an outboard motor.

A small boat is powered by an outboard motor of variable power P. The graph below shows the variation with speed v of P when the boat is carrying different loads.

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.04.03.53.02.52.01.51.00.50.0

350 kg

300 kg

250 kg

200 kg

P / kW

v / ms–1

The masses shown are the total mass of the boat plus passengers,

(a) For the boat having a steady speed of 2.0 m s–1 and with a total mass of 350 kg

(i) use the graph to determine the power of the engine.

........................................................................................................................... (1)

(ii) calculate the frictional (resistive) force acting on the boat.

...........................................................................................................................

........................................................................................................................... (2)

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Consider the case of the boat moving with a speed of 2.5 m s–1

.

(b) (i) Use the axes below to construct a graph to show the variation of power P with the total mass W.

200 250 300 350 400 450W / kg

(6)

(ii) Use data from the graph that you have drawn to determine the output power of the motor for a total mass of 330 kg.

........................................................................................................................... (1)

(Total 10 marks)

5. Data analysis question

At high pressures, a real gas does not behave as an ideal gas. For a certain range of pressures, it is suggested that the relation between the pressure P and volume V of one mole of the gas at constant temperature is given by the equation

PV = A + BP

where A and B are constants.

In an experiment to measure the deviation of nitrogen gas from ideal gas behaviour, 1 mole of nitrogen gas was compressed at a constant temperature of 150 K. The volume V of the gas was measured for different values of the pressure P. A graph of the product PV of pressure and volume was plotted against the pressure P and is shown below. (Error bars showing the uncertainties in measurements are not shown).

13

12

11

105.0 150 10 20

PV / ×10 N m2

P / ×10 Pa6

(a) Draw a line of best fit for the data points. (1)

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(b) Use the graph to determine the values of the constants A and B in the equation

PV = A + BP.

Constant A ……………………………….................................................................

……………………………….................................................................

……………………………….................................................................

Constant B ……………………………….................................................................

……………………………….................................................................

……………………………….................................................................

………………………………................................................................. (5)

(c) State the value of the constant B for an ideal gas.

..................................................................................................................................... (1)

(d) The equation PV = A + BP is valid for pressures up to 6.0 × 107 Pa.

(i) Determine the value of PV for nitrogen gas at a pressure of 6.0 × 107 Pa.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(ii) Calculate the difference between the value of PV for an ideal gas and nitrogen gas when both are at a pressure of

6.0 × 107 Pa.

...........................................................................................................................

...........................................................................................................................

........................................................................................................................... (2)

(e) In the original experiment, the pressure P was measured to an accuracy of 5% and the volume V was measured to an accuracy of 2%. Determine the absolute error in the value of the constant A.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

(Total 14 marks)

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6. This question is about an electrostatics experiment to investigate how the force between two charges varies with the distance between them.

A small charged sphere S hangs vertically from an insulating thread as shown below.

S

A second identically charged sphere P is brought close to S. S is repelled as shown below.

P S force F

r

The magnitude of the electrostatic force on sphere S is F. The separation between the two spheres is r.

(a) On the axes below draw a sketch graph to show how, based on Coulomb’s law, you would expect F to vary with .1

2r

F

0 0 1

2r (2)

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Values of F are determined for different values of r. The variation with 2

1

r of these values is shown below. The estimated

uncertainties in these values are negligible.

F / -10 3 N 7.0

6.0

5.0

4.0

3.0

2.0

1.0

0.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0

110

2

3 2

r/ -m

(b) (i) Draw the best-fit line for these data points. (2)

(ii) Use the graph to explain whether, in the experiment, there are random errors, systematic errors or both.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (3)

(iii) Calculate the gradient of the line drawn in (b) (i).

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (2)

(iv) The magnitude of the charge on each sphere is the same. Use your answer to (b) (iii) to calculate this magnitude.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (4)

(Total 13 marks)

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7. This question is about the rise of water in a capillary tube.

A capillary tube is a tube that is open at both ends and has a very narrow bore. A capillary tube is supported vertically with one end immersed in water. Water rises up the tube due to a phenomenon called capillary action. The water in the bore of the tube forms a column of height h as shown below.

narrow bore

glass wall glass wall

h

water

(a) The height h, for a particular capillary tube was measured for different temperatures of the water. The variation with temperature of the height h is shown below. Uncertainties in the measurements are not shown.

17

16

15

14

13

12

11

10

9.0

8.09080706050403020100

h / cm

C

(i) On the graph above, draw a best-fit line for the data points. (1)

(ii) Determine the height h0 of the water column at temperature = 0C.

.........................................................................................................................

......................................................................................................................... (1)

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(b) Explain why the results of this experiment suggest that the relationship between the height h and temperature is of the form

h = h0(1 − k)

where k is constant.

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (4)

(c) Deduce that the value of k is approximately 4.8 10−3 deg C−1.

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (3)

(d) The experiment is repeated using tubes with bores of different radii r but keeping the water temperature constant. The

graph below shows the variation with r

1 of the height h for capillary tubes of different radii r for a water temperature of

20C.

0.35

0.30

0.25

0.20

0.15

0.10

0.05

025.020.015.010.05.00

h / m

/ 10 m1r–

3 –1

It is suggested that capillary action is one of the means by which water moves from the roots of a tree to the leaves. A particular tree has a height of 25 m.

Use the graph to estimate the radius of the bore of the tubes that would enable water to be raised by capillary action from ground level to the top of the tree. Comment on your answer.

Estimate: .................................................................................................................

.................................................................................................................

Comment: .................................................................................................................

................................................................................................................. (4)

(Total 13 marks)

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8. This question is about a spider’s web.

An experiment was carried out to measure the extension x of a thread of a spider’s web when a load F is applied to it. The results of the experiment are shown plotted below. Uncertainties in the measurements are not shown.

F / 10 N –2

–2x / 10 m

threadbreaks atthis point

9.0

8.0

7.0

6.0

6.0

5.0

5.0

4.0

4.0

3.0

3.0

2.0

2.0

1.0

1.00.0

0.0

(a) Draw a best-fit line for the data points. (1)

(b) When a load is applied to a material, it is said to be under “stress”. The magnitude P of the stress is given by

A

FP

where, A is the area of cross-section of the sample of the material.

Use the graph and the data below to deduce that the thread used in the experiment has a greater breaking stress than steel.

Breaking stress of steel = 1.0 109 N m−2

Radius of spider web thread = 4.5 10−6 m

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (3)

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(c) In a particular web, one thread has the same original length as the thread used in the experiment. In the making of this

web, the original length of the thread is extended by 2.4 10−2 m.

(i) Use the graph to deduce that the amount of work required to further extend the thread to the length at which it

just breaks, is about 1.6 10−3 J. Explain your working.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (3)

(ii) If the thread is not to break due to the impact of a flying insect, then the thread must be capable of absorbing all the kinetic energy of the insect as it is brought to rest by the impact. Determine the impact speed that an insect of mass 0.15 g must have in order that it just breaks the thread.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (3)

(Total 10 marks)

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9. A hot object may be cooled by blowing air past it. This cooling process is known as forced convection. In order to investigate forced convection, hot oil was placed in a metal can. The can was placed on an insulating block and air was blown past the can, as shown below.

thermometer

lid

hot oil

metal can

insulating block

stirrer

current of air

The hot oil was stirred continuously and its temperature was taken every minute as it cooled. The graph below shows the variation with time of the temperature of the cooling oil.

tem

pera

ture

/ C

0 2 4 6 8 10 12 14

time / minutes

120

100

80

60

40

20

0

It is thought that the rate R of decrease of temperature depends on the temperature difference between the oil and its surroundings (the excess temperature θE). The temperature of the surroundings was 26C.

(a) On the graph above,

(i) draw a straight-line parallel to the time axis to represent the temperature of the surroundings; (1)

(ii) by drawing a suitable tangent, calculate the rate of decrease of temperature, in C s–1

, for an excess temperature of 50 Celsius degrees (C).

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

......................................................................................................................... (4)

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(b) In order to investigate the variation with R of E, a graph of R against E is plotted. The graph below shows four plotted data points. Uncertainties in the points are not included.

R / C s–1

E / C

0.24

0.20

0.16

0.12

0.08

0.04

0.00100806040200

(i) Using your answer to (a)(ii), plot the data point corresponding toE = 50C.

(1)

(ii) The uncertainty in the measurement of R at each excess temperature is 10. On the graph, draw error bars to represent the uncertainties in R at excess temperatures of 20C and 81C.

(2)

(c) Explain why the graph in (b) supports the conclusion that the excess temperature E is related to the rate of cooling R by the expression

R = kE ,

where k is a constant.

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (3)

(Total 11 marks)

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10. The question is about investigating a fireball caused by an explosion.

When a fire burns within a confined space, the fire can sometimes spread very rapidly in the form of a circular fireball. Knowing the speed with which these fireballs can spread is of great importance to fire-fighters. In order to be able to predict this speed, a series of controlled experiments was carried out in which a known amount of petroleum (petrol) stored in a can was ignited.

The radius R of the resulting fireball produced by the explosion of some petrol in a can was measured as a function of time t. The results of the experiment for five different volumes of petroleum are shown plotted below. (Uncertainties in the data are not shown.)

25

20

15

10

5

0706050403020100

R / m

30 10 m–3 3

25 10 m–3 3

15 10 m–3 3

10 10 m–3 3

5.0 10 m–3 3

t / ms

Key:

(a) The original hypothesis was that, for a given volume of petrol, the radius R of the fireball would be directly proportional to the time t after the explosion. State two reasons why the plotted data do not support this hypothesis.

1. .........................................................................................................................

.........................................................................................................................

2. .........................................................................................................................

......................................................................................................................... (2)

(b) The uncertainty in the radius is 0.5 m. The addition of error bars to the data points would show that there is in fact a systematic error in the plotted data. Suggest one reason for this systematic error.

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (2)

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(c) It is known that the energy released in the explosion is proportional to the initial volume of petrol. A hypothesis made by the experimenters is that, at a given time, the radius of the fireball is proportional to the energy E released by the explosion. In order to test this hypothesis, the radius R of the fireball 20 ms after the explosion was plotted against the initial volume V of petrol causing the fireball. The resulting graph is shown below.

15

10

5

035302520151050

R / m

V / 10 m–3 3

The uncertainties in R have been included. The uncertainty in the volume of petrol is negligible.

(i) Describe how the data for the above graph are obtained from the graph in (a).

.........................................................................................................................

......................................................................................................................... (1)

(ii) Draw the line of best-fit for the data points. (2)

(iii) Explain whether the plotted data together with the error bars support the hypothesis that R is proportional to V.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

(2)

(d) Analysis shows that the relation between the radius R, energy E released and time t is in fact given by

R5 = Et2.

Use data from the graph in (c) to deduce that the energy liberated by the combustion of 1.0 10–3 m3 of petrol is about 30 MJ.

...................................................................................................................................

...................................................................................................................................

...................................................................................................................................

................................................................................................................................... (4)

(Total 13 marks)

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MARK SCHEME! 1. (a) reasonable scale and axes labelled;

The graph must occupy at least half the grid.

plots correct to within 21 square; 3

Award [2] if correct , [1] for one error and [0] for two or more errors

(b) (i) reasonable curve from 0°C to 10°C; 1

Expect smooth single line within one square of each correctly plotted point.

(ii) 3800 50; 2630 20; 2

Allow ecf from candidate’s graph.

(c) correct line drawn; 1

(d) (i) value correct from graph, 6.2°C; 1

Allow 21 square.

(ii) error is 1.0°C;

% error =

2.5

1 × 100;

= 19%; 3

Allow “bald” correct answers.

Award [2] if

6.2

1 × 100 = 16% is used – or candidate’s figures.

2. (a) a straight line; through the origin; 2 max

(b) any straight line; that fits within ALL the error bars; 2 max

1.40

1.20

1.00

0.80

0.60

0.40

0.20

0.000.00 0.50 1.00 1.50 2.00 2.50

Weight / N

acceleration/ ms–2

(c) (i) a systematic error is when every data point deviates from the “correct” value; by the same fixed amount as seen by intercept on graph / OWTTE; 2 max

Accept answers that explain by giving an example of a possible systematic error eg friction.

(ii) 0.3 N; 1

Accept 0.25 N 0.35 N. NB Watch for use of wrong axis!

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(iii) realization that mass = (gradient)–1

;

Award this mark for full Newton II equation (with friction)

to give mass = 1.4 kg (Accept 1.2 kg 1.6 kg.); 2 max

Use of F = ma for 1 data point receives [0] (unless candidate’s line is through origin). Watch for ecf from candidate’s own line.

[9]

3. (a) 200

175

150

125

100

75

50

25

00 10 20 30 40 50 60

Q / nC

V / V

half area of graph paper at least to be used; axes labels including units; scale; data points; ((0, 0) need not be included) 4

(b) best fit line need not go through origin; 1

(c) use of at least half the line / algebraic indication;

value = 3.6 or 3.6 × 10–9

; 2

(d) C V–1; 1

(e) recognize that the gradient m = d

A0 ;

therefore 0 = A

dm;

substitute to get ε0 = 9.0 × 10–12 C V–1 m–1 (C2 N–1 m–2 – data book unit or F m–1); 3 [11]

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4. (a) (i) 2.0 kW; ( 0.10 kW) 1

(ii) F = v

P;

= 1000 N = ; ( 50 N) 2

(b) (i) 4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0.0200 250 300 350 400

P / kW

W / kg

sensible use of grid and suitable P scale; (at least half of grid used) labelled P axis with correct units; data point (200, 0.65); data point (250, 0.95); data points (300, 1.9), (350, 3.1);

Allow 0.2 kW.

line of best fit; 6

(ii) 2.6 kW; (0.1 kW) (watch for ecf) 1 [10]

13

12

11

100 5.0 10 15 20

P / ×10 N m6

2

–2

PV / ×10 N m

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5. (a) suitable straight-line of best fit; 1

(b) A is the intercept on the y-axis consistent with line drawn (or by implication);

= 12.6 = 1.3 × 103

Nm – the best fit line should give a 2 SD

value of 1.3 × 103

Nm; B is the gradient; some evidence that reasonable values have been used (y2 – y1 > 0.9, x2 – x1 > 8);

= –1.0(0.1) × 10–5

; 5

Accept answers based on using two data points on line. Award [3 max] if points not on line. Ignore any missing units and do not penalize if minus sign is omitted. Award [1] for determination of B if only one data point is used.

(c) B = 0; 1

(d) (i) substitute into PV = A + BP

PV = 1300 – (1.0 × 10–5

× 6.0 × 107

); = 700(640 760)Nm; 2

= 1.9(0.5) × 103

Nm if BP is added instead of subtracted.

Award [1] for ecf.

(ii) recognize that the ideal gas value is the intercept on the y-axis; or from PV = RT; or = constant A;

difference 600(540 660) Nm; 2

(e) error bars constructed on two well separated points; attempt to draw reasonable extreme graph line / lines; reasonable estimate of uncertainty; Accept alternative approach. total% error for PV = 7%;

7% of 12.6 × 102

= 0.9 × 102

;

so absolute error = (0.9) × 102

N m; 3 [14]

6. (a) any line (curve) through the origins;

straight-line; 2

(b) (i) a straight-line (drawn with ruler); which is appropriate ie does not or would not go through the origin; 2 Award [0] if points joined “dot to dot”.

(ii) data subjected to both types of error; Can be implied in subsequent answer. random since points are scattered above and below the line; systematic since line does not / would not go through origin; 3

Accept answers that get this general idea across but do not accept answers tha try to explain the source of the error without naming type of error.

Award [2 max] for answers that confuse random with systematic but are otherwise correct. Award [1 max] for stating that there is only one type of error with correct explanation.

(iii) use of “large triangle” for gradient (seen or implied); Hypotenuse of triangle used should be at least half the distance

between the first and the last point on the graph ie 5 cm.

to get gradient = 0.59 106

= 5.9 107

; 2 Ignore any units. Award [1 max] for 0.59 without power of ten.

Accept from 5.3 to 6.5 107

.

Award [0] if using a single point unless student’s line goes through that point and the origin as well. Award [0] if using two data points as opposed to the gradient unless both data points are on candidate’s line.

(iv) use of Coulomb’s law (seen or implied);

correct identification of gradient = kq1 q2 = k q2

;

q2

= 6.56 1017

C2

;

q = 8.1 109

C; 4

Award [3 max] for a bald answer without any working. Award [1 max] if the candidate uses a point on the graph to calculate q.

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21

17. (a)

(i) sensible line of fit with reasonable distribution of points either side of line; 1

(ii) h0 = 16.2 (0.2)cm; 1

(b) this is a straight-line graph so has equation of the form y = mx + c;

h = h0 (1 k) gives h = h0 h0k;

m = h0k; c = h0; 4

essentially look for: stating equation of a straight-line graph, showing that h = h0 (1 k)

can be written in this form, identifying m and c.

(c) .

;gradient

0 s correcttatement i if this sn be giventhen it ca

n in (b) been give k has nothfor mIf credit

hk 0

gradient = 0.077 ( 0.003);

therefore, ;2.16

077.0k

4.8 103

deg C1

Or

Allow use of a point on line of best fit ie choice of data point from line of best fit; correct substitution into h = h0(1 k);

correct rearrangement essentially showing that ;)1(1

0h

h

θk 3

Accept range of answers for the gradient between 4.9 103

and 4.6 103

.

(d) estimate:

;gradient

rh

gradient = 1.5 ( 0.2) 105

;

;m108.00.625

105.1 75

r

Comment: this is very small so it is unlikely that capillary action is the only

mechanism / OWTTE / this assumes that the direct proportion holds for values of h up to 25m / OWTTE; 4

Accept ecf based on estimate only if comment is reasonable and consistent. If numerical value is correct, then award the mark for a plausible explanation (eg reference to molecular forces) as to why this is a reasonable value.

[13]

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22

8. (a)

correct line of best fit; 1

The line should go through a majority of the points.

(b) from the graph breaking load = 8.5(0.1) 102 N;

breaking stress =

Pa103.1105.414.3

105.8 9

122

2

or Nm2

;

some statement of conclusion; 3

(c) (i) work = area under graph;

between (2.4 102 , 1.6 102) and (5.6 102 , 8.5 102);

;109.62.3102.36.1 4214

= 1.6 103

J

If incorrect line of best fit in (a), allow first marking point only.

or

work = average force distance / displacement / extension;

average force = 5.1 102 N;

extension = 3.2 102 m;

to give1.6 103 J 3

(ii) KE of insect = work needed to break web = 1.6 103

J;

;KE2

mv

;ms6.4105.1

102.3 14

3

3

No ecf from (c)(i) ie the value 1.6 103 J must be used. [10]

Page 23: IB Physics Review-Measurement - Wikispaceswsscience.wikispaces.com/file/view/IB+Physics+Review-Measureme… · IB PHYSICS HL REVIEW PACKET: ... (4) (b) Draw the line of ... In the

23

9.

(a) (i) line in correct position from t = 0 to t =14 min; 1

Allow 21 square.

(ii) reasonable tangent drawn at correct position ie at 76C but allow 70C 85C;

If tangent position is not acceptable, award [1 max] in this section for length of tangent. line length used for tangent at least 8 cm; value 0.09 0.13; accuracy value within 0.10 0.12; 4

Award [1] for value between 10% and 20% of 0.11 and [2] for value 0.11 10%.

Unit of answer is not required. If the candidate fails to convert to

s1

, then award one of the last two marks for answer in range

6.0 7.2C min1 .

(b)

(i) point plotted correctly; (allow ecf from (b)) 1

(ii) error bar at E = 20C: 4( 2)mm long;

error bar at E = 81C : 20( 4)mm long; 2

Ignore any horizontal error bars.

(c) allowing for uncertainties in readings; points lie on straight-line; and line passes through origin; 3 Award [1] for “last point off line, so not obeyed”.

[11]

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24

10. (a) 1: the lines do not go through the origin;

2: the lines are not straight (lines) / gradient is not constant; 2 Award full marks if the candidate combines the two statements.

(b) the petrol is stored in cans / initial volume of petrol not taken into account; the radius at t = 0 is probably the size / radius of the can;

or

difficulty in measuring R; some comment as to the whereabouts of the zero point in the experiment; 2

(c) (i) by reading the value of R at t = 20 ms for each of the five lines / OWTTE; 1

(ii) smooth curve with an intercept of R = 5.0(1.0)m; and does not go outside error bars; 2

(iii) no the line is not a straight-line; even with the error bars it cannot be made to be a straight-line / OWTTE; 2 Award [0] if “no” and incorrect explanation or if there is no explanation.

(d) choice of suitable data point in the range V = 5 15

eg R = 10.5 for 10 103 m3;

;2

5

t

rE

;10320

1020

5.10 623

5

divide by 10 / other chosen value of V;

30 MJ for 1.0 103 m3 4 [13]


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