11STST EXAMINATION EXAMINATION

COVER 2 CHAPTERCOVER 2 CHAPTER CHAPTER 1& 2CHAPTER 1& 2

1.2 UNDERSTANDING BASE 1.2 UNDERSTANDING BASE QUANTITIES AND DERIVED QUANTITIES AND DERIVED QUANTITIESQUANTITIES

Physical Quantity

Physical characteristic that can be measured

Base Quantities Derived Quantities

BASE QUANTITYBASE QUANTITYQuantities that cannot be Quantities that cannot be defined in terms of other defined in terms of other base quantities (5 only)base quantities (5 only)

DERIVED QUANTITYDERIVED QUANTITYPhysical quantities derived by combining base Physical quantities derived by combining base

quantities by multiplication, division or both.quantities by multiplication, division or both.

1.3 UNDERSTANDING SCALAR 1.3 UNDERSTANDING SCALAR AND VECTOR QUANTITIESAND VECTOR QUANTITIES

SCALAR QUANTITYSCALAR QUANTITY

Quantities that have Quantities that have magnitude but no magnitude but no directiondirection

VECTOR QUANTITYVECTOR QUANTITY

Quantities that have Quantities that have both magnitude and both magnitude and directiondirection

Consistency, Accuracy and Consistency, Accuracy and SensitivitySensitivity

How to improve accuracyHow to improve accuracy

Take reading twice or more and the average Take reading twice or more and the average value are calculatedvalue are calculated

Avoid parallax errorAvoid parallax error Avoid zero errorAvoid zero error Use high accuracy measuring instrumentUse high accuracy measuring instrument

PARALLAX ERRORIt occurs because the position of the eye

is not perpendicular to the scale of the instrument.

How to avoid parallax error ?How to avoid parallax error ?

1)1) To avoid ,position of the eye must be To avoid ,position of the eye must be in line with the reading to be takenin line with the reading to be taken

2)2) To overcome parallax errors in To overcome parallax errors in instruments with a scale and pointer, instruments with a scale and pointer,

e.g. an ammeter it is often useful to e.g. an ammeter it is often useful to have a mirror behind the pointer. have a mirror behind the pointer.

Vernier Calliper Vernier Calliper

Main scale

Vernier scale

Vernier Callipers reading = Main scale + Vernier scale = 2.7 + 0.06 = 2.76 cm

Find zero errorFind zero error

Zero error = + 0.02 cm

Read the measurement.Read the measurement.Find the correct readingFind the correct reading

Observed Reading = main scale + vernier scaleObserved Reading = main scale + vernier scale

= (0.4 + 0.09) cm= (0.4 + 0.09) cm

= 0.49 cm = 0.49 cm

Corrected reading = observed reading – zero errorCorrected reading = observed reading – zero error

= 0.49 – (+ 0.02) cm= 0.49 – (+ 0.02) cm

= 0.47 cm= 0.47 cm

Micrometer Screw GaugeMicrometer Screw Gauge

Ratchet Knob =Prevent the user from exerting too much pressure

Positive zero errorPositive zero error

2 divisions below horizontal reference

Positive Zero error = + 0.02 mm

Negative zero errorNegative zero error

3 divisions above horizontal reference

Negative Zero error = - 0.03 mm

PENDULUM EXPERIMENTPENDULUM EXPERIMENTInferenceInference The period of a simple pendulum is The period of a simple pendulum is

depends on its lengthdepends on its length

HypothesisHypothesis The longer is the pendulum The longer is the pendulum

the longer is the period of its the longer is the period of its oscillationoscillation

AimAim To Investigate the relationship To Investigate the relationship between length and period of a simple between length and period of a simple pendulum.pendulum.

Variable:Variable:

Manipulated Manipulated

RespondingResponding

FixedFixed

-Length of the pendulum, -Length of the pendulum, ll

-Period of the pendulum, T-Period of the pendulum, T

-Mass of the pendulum bob, m-Mass of the pendulum bob, m

List of List of apparatus apparatus and materialand material

Retort stand, coin,plasticineRetort stand, coin,plasticine

pendulum bobpendulum bob

Retort stand

coin

pendulum

ProceduresProcedures 1.1. Set up the apparatus as shown in the Set up the apparatus as shown in the figure above.figure above.

2.2. Measure the length of the pendulum,l Measure the length of the pendulum,l = 90.0 cm by using a meter rule.= 90.0 cm by using a meter rule.

3.3. The bob of the pendulum was The bob of the pendulum was displaced and released.displaced and released.

4.4. Time of 20 oscillations is Time of 20 oscillations is measured by using a stop watch. measured by using a stop watch.

5. Repeat the timing for another 20 5. Repeat the timing for another 20 oscillations. Calculate the average oscillations. Calculate the average time.Period = time.Period = tt oscillations oscillations

2020

6.6. Repeat steps 2, 3 and 4 using l = Repeat steps 2, 3 and 4 using l = 50.0 cm, 60.0 cm, 70.0 cm 50.0 cm, 60.0 cm, 70.0 cm and and 80.0 cm80.0 cm

IMPORTANT REMINDERIMPORTANT REMINDERWHEN YOU TABULATE DATA!!WHEN YOU TABULATE DATA!!

BEWARE WITH…BEWARE WITH…

IMPORTANT REMINDERIMPORTANT REMINDERWHEN YOU TABULATE DATA!!WHEN YOU TABULATE DATA!!

BEWARE WITH…BEWARE WITH…

HOW TO TABULATE DATAHOW TO TABULATE DATA

Length of Length of pendulumpendulum, l(cm), l(cm)

Time taken for 20 Time taken for 20 complete complete oscillation, t(s)oscillation, t(s)

Period ,TPeriod ,T

=t /20 (s)=t /20 (s)

TT2 2 (s(s22))

t 1t 1 t 2t 2 Mean,tMean,t

90.090.0

80.080.0

70.070.0

60.060.0

50.050.0

1)All data for manipulated and respondingvariable must follow the accuracy of the instrument

2)mean,t can be calculated using formula (t1 + t2)/2 .the answer can be 2 or 3 decimal place

Manipulated at first column

Responding at second column(depends on question)

1) Correct symbols and unit !!1) Correct symbols and unit !!

Length of Length of pendulum,pendulum,

l(cm)l(cm)

Time taken for 20 complete Time taken for 20 complete oscillation, t (s)oscillation, t (s)

Period ,Period ,TT

=t /20=t /20

( s)( s)

TT2 2 (s(s22))

t t 11 t t 22 Average,tAverage,t

90.090.0

80.080.0

70.070.0

60.060.0

50.050.0

2) Don’t do calculation in the table!2) Don’t do calculation in the table!

Length of Length of pendulumpendulum,l/cm,l/cm

Time taken for 20 complete oscillation, Time taken for 20 complete oscillation, t/st/s

Period ,T= Period ,T= (t /20 )s(t /20 )s

t 1t 1 t 2t 2 Mean,tMean,t

90.090.0 18.918.9 19.119.1 (18.9 + 19.1) (18.9 + 19.1)

22

= 19.0= 19.0

19.0 19.0 ÷ ÷ 2020

=0.950=0.950

80.080.0 17.917.9 17.917.9 17.917.9 0.8950.895

70.070.0 16.816.8 16.816.8 16.816.8 0.8400.840

60.060.0 15.615.6 15.615.6 15.515.5 0.7750.775

50.050.0 13.913.9 14.114.1 14.014.0 0.7000.700

3) decimal place must be 3) decimal place must be consistent column by column!!consistent column by column!!

Length Length of of pendulupendulum,L/cmm,L/cm

Time taken for 20 Time taken for 20 complete oscillation, t/scomplete oscillation, t/s

Period ,Period ,TT

=t /20 s=t /20 s

TT2 2 (s(s22))

t1t1 t 2t 2 Mean,Mean,tt

90.090.0 19.119.1 1919 19.019.0 0.9500.950

80.080.0 17.917.9 17.917.9 17.917.9 0.8950.895

70.070.0 16.816.8 16.816.8 16.816.8 0.8400.840

60.060.0 15.615.6 15.515.5 15.515.5 0.7750.775

50.050.0 15.615.6 14.014.0 1414 0.7000.700

DiscussionDiscussion Precautions :Precautions :

1.1. Oscillation time is measured Oscillation time is measured when the pendulum attained a when the pendulum attained a steady state.steady state.

2.2. Time for 20 oscillations is Time for 20 oscillations is repeated twice to increase repeated twice to increase accuracy.accuracy.

ConclusiosConclusios The period increases when the The period increases when the length of the pendulum increases. length of the pendulum increases.

Therefore, hypothesis accepted.Therefore, hypothesis accepted.

IMPORTANT REMINDERIMPORTANT REMINDERWHEN YOU PLOT GRAPH!!WHEN YOU PLOT GRAPH!!

BEWARE WITH…BEWARE WITH…

IMPORTANT REMINDERIMPORTANT REMINDERWHEN YOU PLOT GRAPH!!WHEN YOU PLOT GRAPH!!

BEWARE WITH…BEWARE WITH…

1)Title of graph must be shown1)Title of graph must be shown

2) Suitable scale2) Suitable scale

- scale must start from zero- scale must start from zero

- cannot skip scale- cannot skip scale

2) Correct symbols and units2) Correct symbols and units

3) Correct plot3) Correct plot

4) Smooth line4) Smooth line

5)Line passing y-axis (do extrapolation)5)Line passing y-axis (do extrapolation)

6) More than 50% of the graph paper 6) More than 50% of the graph paper

How to analyze the dataHow to analyze the dataa) determine the relationship between a) determine the relationship between

2 variables2 variables

rate of change of distance

rate of change of displacement

ms-1ms-1

Average of speed = Average of speed = total distance travel,s (m)total distance travel,s (m)

time taken,t (s)time taken,t (s)

= ms= ms-1-1

Average of velocity = Average of velocity = total displacement,s(m)total displacement,s(m)

time taken,t(s) time taken,t(s)

= ms= ms-1-1

Method of calculationMethod of calculation

Determination of accelerationDetermination of acceleration

u = 3/0.2 = 15.0cms-1u = 3/0.2 = 15.0cms-1v = 8/0.2 = 40.0 cms-1v = 8/0.2 = 40.0 cms-1 t = (6-1) x 0.2 = 1st = (6-1) x 0.2 = 1s

a =a = v-u v-u tt = = 40.0 – 15.040.0 – 15.0 11 = 25.0 cms= 25.0 cms-2-2

8

7

6

5

4

3

2

1

0

u

v

The equation of motionThe equation of motion

s : displacement, (m)s : displacement, (m)

u : initial velocity (ms-1)u : initial velocity (ms-1)

v : final velocity (ms-1)v : final velocity (ms-1)

a : acceleration(ms-2)a : acceleration(ms-2)

t : time,(s)t : time,(s)

5 important formula5 important formula(must memorize)(must memorize)

tvus )(2

1

t

uva

atuv

2

2

1atuts

asuv 222

ExerciseExercise

The force acted on the trolley is 120 N. The luggage has a The force acted on the trolley is 120 N. The luggage has a mass of 20 kg. mass of 20 kg.

(a) What is the weight of the luggage ? [ 1(a) What is the weight of the luggage ? [ 1 mark mark ]]

(b) In the space below draw the components of force 120 N for(b) In the space below draw the components of force 120 N for

[ 1 [ 1 mark mark ]]

(i) Determine the values of the vertical component [ 2(i) Determine the values of the vertical component [ 2 marks marks ]] (ii) Calculate the force acted on the ground (ii) Calculate the force acted on the ground

(c) If the friction of the ground is 4 N, what is the resultant force of (c) If the friction of the ground is 4 N, what is the resultant force of the horizontal components [ 2 the horizontal components [ 2 marks marks ]]

EXAMPLES 1:EXAMPLES 1: An astronaut has a mass of 75 kg. An astronaut has a mass of 75 kg.

What is his weight if What is his weight if

a)a) He is on the surface of the Earth He is on the surface of the Earth where the gravitational field strength where the gravitational field strength is 9.8 N kgis 9.8 N kg-1 -1 ??

b)b) he is on the surface of the Moon he is on the surface of the Moon where the gravitational field strength where the gravitational field strength is is of that on the surface of the of that on the surface of the Earth?Earth?

6

1

SOLUTION :SOLUTION :a)a) On the surface of the Earth,On the surface of the Earth,

his weight, W = his weight, W = m x gm x g

= = 75 x 9.875 x 9.8

= 735 N= 735 N

b)b) On the surface of the Moon, gravitational field strength, On the surface of the Moon, gravitational field strength, gg

= x 9.8 N kg= x 9.8 N kg-1-1

his weight, W = his weight, W = m x gm x g

= 75 x = 75 x

= 122.5 N= 122.5 N

6

1

6

8.9

The figure shows a marble, a The figure shows a marble, a razor blade and a piece of razor blade and a piece of paper being released at the paper being released at the same time in a vacuum same time in a vacuum cylinder.cylinder.

Which object will reach the Which object will reach the base first?base first?

EXAMPLES 2: (SPM ‘ 03)

ANSWER 2:ANSWER 2:

All three objects will reach the base at All three objects will reach the base at the same time.the same time.

( all three objects are falling with the ( all three objects are falling with the same same gravitational accelerationgravitational acceleration))

A stone is dropped from a height of 8 m A stone is dropped from a height of 8 m above the surface of the Moon. Calculate above the surface of the Moon. Calculate the time taken for the stone to reach the the time taken for the stone to reach the surface of the Moon.surface of the Moon.

[Moon’s gravitational acceleration = of [Moon’s gravitational acceleration = of Earth’s gravitational acceleration]Earth’s gravitational acceleration]

Solution:Solution:6

1

EXAMPLES 3: (SPM ‘ 03)

ss = = ut + gtut + gt22 2

1

SOLUTION 3:SOLUTION 3:ss = = ut + gtut + gt22

8 = 0 + X X 9.8 X 8 = 0 + X X 9.8 X tt22

t =t = 3.13 s 3.13 s

2

1

6

12

1

Answer…Answer…

a) speed is the rate of distance travelled a) speed is the rate of distance travelled (1m)(1m)

b)the speed limit is to reduce the momentum b)the speed limit is to reduce the momentum of heavy vehicles to ensure that they are of heavy vehicles to ensure that they are able to stop within a safe distance during the able to stop within a safe distance during the accidentsaccidents

Design toy carDesign toy car (ii) Using the suitable physics concepts, you are required to give (ii) Using the suitable physics concepts, you are required to give

some some suggestions on designing a toy car. Explainsuggestions on designing a toy car. Explain your suggestions based on theyour suggestions based on the following aspects ;following aspects ; - density of the toy car parts- density of the toy car parts - engine power- engine power - spring in suspension system- spring in suspension system - size of tyre- size of tyre - the designs of the spring- the designs of the spring

[10 [10 marksmarks]]

  

Modification ExplanationLow density of motorcyclepartsSo that it is lighterHigh engine power To produce high acceleration//high resultant forceHigh spring constant // stifferspringSo that the spring is stiffer //motorcycle bounce less // lessvibrationWide tyre // smooth tyre To increase stability // to reducefriction8Total

Wish u all,Wish u all,

All the best…All the best…& &

Good luck!!! Good luck!!!