Physics 30 Final Review
Unit 1 ‐ Kinemacs and Dynamics
‐Know how to idenfy the bolded terms in this unit. Since there is no wring on the final, you just need to have a working knowledge of these terms. Not memorizaon usually.
‐d‐t and v‐t graphs are important, so know how to solve problems with each type and the differences between them
d (m) t (s)
109
N
S
5
8
1427
a) What is the velocity at 12 seconds?
b) What is the posion of the object at 24 second?
c) What is the average velocity of the whole trip?
d) What is the average speed of the whole trip?
Slope Area Distance Displacement
dt graph
Speed or Velocity (direction counts)
N/ADifference between starting point and end point
Difference between starting point and end point (direction counts)
vt graph Acceleration
Distance or displacement (direction counts)
Area of vt graph (direction doesn't matter)
Area of vt graph (above xaxis is positive, below is negative)
v (m/s) t (s)
109
N
S
5
8
1427
a) At what me(s) is the velocity 4 m/s?
b) What is the total displacement of the trip?
Word problems:
‐Recall that somemes they can be solved easily using one of the four magic formulas, but somemes a combinaon of more than one formula is needed, and somemes drawing a v‐t graph is really helpful.
Example:
An object inially moving 6.00 m/s accelerates at 4.00 m/s 2. Calculate:
a) me to reach a speed of 12.0 m/s.
b) speed at 2.00 s.
c) distance moved in 5.00 s.
d) distance moved in third second.
More challenging examples:
A car moving at 2.00 m/s accelerates at 6.00 m/s2. Calculate the me it takes to travel the first 56.0 m from the point where it started to accelerate.
An object inially moving at a velocity, V, accelerates at 4.50 m/s 2 tripling its velocity while traveling a distance of 72.0 m.
a) What is V?
b) How long does it take the object to travel the 72.0 m?
.
Vectors
‐have both magnitude and direcon
‐You can solve them however you want to on the final (graphically or mathemacally) but my recommendaon is to know how to solve them mathemacally by breaking them down into components
Example:
A boat is travelling [N 30o E] at 35.0 km/hr for 3 hours. It then turns and heads [S 45o W] for 2 hours. How far and in what direcon is the boat from it's starng point?
A car is travelling 100 km/hr [NE] and then turns and accelerates to 100 km/hr [E 20o S]. This takes 2 minutes to accomplish. What is the car's acceleraon during this me?
‐Also, know the difference between adding and subtracng vectors if only a picture is given
Example:
Add Subtract
Newton's Laws of Moon
There always seems to be a queson just on Newton's Laws (ie. Newton's second law states _______)
Inera is also an important term to understand. It is an object's tendency to resist changes in moon. For example, a train has a large amount of inera because it is hard to get moving, and once it is moving it is hard to stop.
Most of the quesons will be F=ma quesons in some form or another.
Recall that when you are looking at a system, there is FA FF and FNet
FNet = FA + FF (and Fricon is always acng against F A)
When an object is moving, and an acceleraon is given, we can find F Net by using F=ma
Usually, there are a few F=ma problems. They can involve the four magic formulas, and somemes use vectors as well
Examples:
A 4.00 kg object is accelerang at 3.00 m/s 2 on a friconless surface. What amount of force was given to the object?
A 3.50 kg object starts at rest and is pushed by a force of 10.0 N. The amount of fricon on the surface is 2.50 N. How far does the object move in 15.0 seconds?
FF = 5.00 N
3.00 N 400
The wagon below is being pulled at a 40o angle with 15.0 N, and also has 5.00 N of Fricon and a 3.00 N force pulling in the opposite direcon. The wagon weighs 7.50 kg. How far will it have moved in one minute?
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Weight and Mass
Recall that weight and mass are not the same thing
Weight is the amount of force that gravity exerts on an object. Thus it can change, depending on how much gravity is pulling on you (ie. If you are in space, you are weightless)
Mass is the amount of maer that an object has. On Earth, mass and weight are used interchangeably, but be sure to know that they are different.
Weight is found by the formula Fg = mg. Where g = ‐9.80 N/kg
Example
How much does a 75.0 kg person weigh on Earth?
How much would that person weigh on Mars where g = 3.6 N/kg?
I have never seen "elevator" quesons on the final, but they might be a good thing to review, just in case there is one like it and you would have an idea what to do.
For a quick review, the elevator problems used the following principle:
Fnet = Fg + Fnormal
Recall that Fnormal is the force that is pushing up on us at all mes to keep us from falling to the center of the Earth. If Fnormal is greater than Fg we accelerate upwards. If Fnormal is less than Fg we accelerate downwards.
.
Free Fall
When an object is dropped or shot straight in the air, the only forces acng on it are gravity and air resistance.
Luckily for us, we will neglect air resistance when making calculaons, so the only force we need to worry about is gravity.
So we know that acceleraon is 9.80 m/s 2
When an object is falling, it is easiest to use +9.80 m/s2 because the moon and acceleraon are in the same direcon (down) .
Examples
An object is dropped from a height of 255 m. How fast will it be falling when it hits the ground?
One object is dropped from rest out of a window 125 m above the ground, while a second is thrown downwards at 5.50 m/s. How many seconds would you have to wait to throw the second object so they hit the ground at the same me?
When an object is being shot straight up, it is easiest to use ‐9.80 m/s2 because the moon and acceleraon are in opposite direcons .
Examples
A cannon ball is shot straight up at 75.0 m/s. How high will the cannon ball reach?
A baseball is hit straight upwards at 15.0 m/s off the bat. How many seconds will a player have to catch it before it hits the ground?
The only me we will deal with air resistance is when discussing terminal velocity. I haven't seen any quesons dealing with terminal velocity, but it doesn't hurt to know.
Terminal velocity is the point where the force of gravity and the force of air resistance equal out, therefore causing the object to stop accelerang.
Unit 2 ‐ Mechanical Energy
WorkWork is really a change in energy. When work is done on an object, the amount of energy that object has is either increased or decreased. Since work has to do with energy the unit that goes along with work is the Joule
There are many formulas for energy, but they are mostly just derivaons of each other.These are the two most commons formulas we use, and then change them as we need.
W = FdW = ∆E
There are three condions that have to be met in order for work to be done
1) There must be a force exerted on the object
2) The object must move due to the force
3) The moon of the object must be parallel to the force on the object
Know these three properes, because there is always a queson on them.
Usually, there is a queson with something that doesn't move, or has centripetal moon (force is perpendicular to the moon, therefore no work is done)
Example:A 25.0 kg crate is pulled 15.0 m by a 75.0 N force with a handle that makes a 30o angle with the ground. How much work is being done to the crate?
PowerThe rate at which work is done. The unit for this is the same as the unit later on, which is Was (J/s).
P = W or P = ∆Et t
A Wa is a prey small unit of energy, so oen a kiloWa (kW) is used. When talking about vehicles, horsepower is used, which is about 746 W. Horsepower is not on the departmental.
Example:
A worker at a seed plant lis 45.0 kg bags 1.50 m up to a conveyor belt. If they can do this on average 50.0 mes in a minute, how much power are they producing in that minute?
.
Kinec EnergyThe energy that an object has when it is moving is its kinec energy .
EK = 1/2 mv2
EK or KE mean the same thing. Departmental formula sheet uses EK
Example:A 150 kg mass moving with an inial velocity of 15.0 m/s accelerates to 18.0 m/s aer an addional force is applied to it. How much energy is given to the object to increase its speed to 18.0 m/s?
Calculate the inial velocity of a 4.00 kg mass if aer being pushed a distance of 15.0 m by a 5.70 N force it ends up with a velocity of 7.00 m/s.
Gravitaonal Potenal EnergyPotenal energy is stored energy. It has the ability to be changed into other forms of energy (kinec energy in this secon) , but it is not yet in the form of kinec energy.
Ep = mgh or Eg (which is on the formula sheet)An example of this is a dam that holds back water. The water has a great amount of potential energy because it is at a higher level than the valley below. Once the wall is removed, the water can fall down and start building kinetic energy.
All Ep
Some Ep and some Ek
All Ek but being converted into electricityExample:
How high is a 3.50 kg ball off the ground if the total energy of the ball is 805 J and the ball has fallen for 1.50 seconds?
Etot = Ep
Etot = Ep + Ek
Etot = Ek
On the departmental, these problems will oen be applied to roller coasters, or a ball on a friconless track. There are a few of these different ones on the pracce departmentals, so if you see them, use this type of thinking to solve the problem.
Unit 3 ‐ ElectricityElectrostacs
Know the three fundamental laws of electric charges (always a queson on these)
1) Like charges repel2) Opposite charges aract3) Charged objects are aracted to neutral objects
Know how to convert between Coulombs and elementary charges Q = Ne
ExampleA parcle has 2.50 x 10 5 el ch. What is the charge of this parcle?
Know how to use Coulomb's Law
F = kQ1 Q2
d2
Remember that there are two different constants8.99 x 109 if you are using Coulombs and 2.31 x 10‐28 if you are using el ch
ExampleWhat is the force of aracon between the two charges?
4.50 x 104 m
12500 el ch 1.75 x 103 C
Current
Current is how many coulombs pass by a point every second. This is measured in Amperes, or Amps.
Alternang current is how our power is transported from power staons to our homes.Direct current is how most of our mobile devices get power. Baeries are the most common example
Formula is I = Q t
Generally, quesons to do with current are either theory based (what is the unit for current , what does it mean, alternang vs. direct) or have to do with circuits, which we will cover later in the review.
Know how to use Q = Ne from above in order to find out how many Coulombs might pass a point in a given amount of me.From 2010 prototype:A student is using a laptop computer for 30.0 minutes. The laptop computer runs on a baery that produces an electric potenal of 20.0 V. Due to the nature of its electrical components, the laptop computer draws a total current of 3.25 A. The number of electrons that leave the negave terminal of the baery during the me the laptop was used is:
Potenal Difference (Voltage)
Understand that voltage is the amount of energy that each Coulomb of charge possesses as it moves through a circuit. The higher the voltage, the more energy that each Coulomb of charge has
There are many formulas for voltage, but again it is more important to understand what voltage is. Most likely the quesons about voltage will come up in circuit analysis.
Power
There may be some quesons to do with calculang power, but there generally are not that many. kW hr quesons, while important in real life because they relate directly to your future power bills, do not usually make an appearance on departmentals.
Examples
How much power is used by a laptop that draws 3.5 amps and has a potenal difference of 20.0 volts?
How much would it cost to run that computer for 24 hours a day, 7 days a week for a year? The cost of one kW hr is 12.5 cents.
Resistance
Know the four properes that determine resistance:1) Cross seconal area2) Length3) Temperature4) Natural Properes of the material
Ohm's Law
V = IR is Ohm's Law. It states that there is a direct relaonship between voltage, current and resistance in a circuit.
High Voltage and high Current would mean a low resistance.Low Voltage and low Current would mean a high resistance. And so on...
V = IR is mostly in the context of circuits, but there are some quesons that are not within a circuit.ExampleWhat is the current if there are 7.50 Ω and 110. V? How much power does it draw?
Circuit Diagrams
Series Parallel Combination
How do I Tell? One path for electrons to follow
Multiple paths for electrons to follow
Series and parallel branches in the same circuit
Current Same everywhere Add up the currentWork from the furthest from the battery back to the battery to find equivalent resistance.
Voltage Add up the voltage Same Everywhere
Resistance Add up the resistance Rt = (1/R1 + 1/R2 ... )1
Also recall Kirchoff's Laws
1) Kirchoff's Current Law ‐ at any juncon in an electrical circuit, the total current flowing into that juncon is the same as the total current leaving the juncon.
2) Kirchoff's Voltage Law ‐ The sum of the voltages at each resistor or juncon is the same as the total voltage of the baery.
It It
It
V1
V2
V1 + V2 = 24.0 V
Example
Find the amount of Voltage for V1 and V2 above
.
More circuits
18.0 V
2.00
1.00
3.00
6.00 8.00
7.00
5.00
110.0 V
R1 = 15.0
V1 = 30.0 V
R2 = 30.0
R3 = ?
V3 = ?
ExampleWhat is V1? What is R1? What is I2?
12.0 VR2 = 5.00
2.00 A
R1 = ?
I2 = ?
V1 = ?
.
ExampleWhat are V3 and R3?
ExampleWhat is Rt? What is the current flowing through the 1.00 ohm resistor?
Unit 4 Nuclear Physics
Things to know very well:
What radioacvity is (spontaneous emission of parcles from a radioacve nucleus)
Alpha, Beta, Gamma radiaon (What are they, what can stop them, which cause a transmutaon)
Which sciensts were involved in the discovery of radiaon (Curies, Becquerel) and what they discovered
Natural background radiaon and other ways that we are exposed to radiaon
The composion of Natural Uranium (99.3% U‐238, 0.7% U‐235)
Which Uranium is used in a CANDU Reactor vs. other Fission Reactors vs. Nuclear Bombs(Natural unrefined) (3‐4% U‐235) (90% U‐235)
CANDU Reactors ‐ Know the name, diagram, and all terms associated with these reactors (always 2‐4 quesons on these)
Other things to know:
Different ways to detect radiaon (Geiger Muller Tube and Photographic Plates are most common)
What a Bq, Gy and Sv are (Bequerel, Gray, Sievert) and what they mean (won't be any calculaon quesons with these, just understand how they are used)
What fission and fusion are (differences between them)
The strong force and how it relates to both fission and fusion
Understand what nuclear mass defect means (the mass of a parent nuclei is different than the sum of the protons and neutrons in it, because it takes energy to put the nucleus together)
Understand the Nuclear Fuel Cycle as it relates to CANDU Reactors
Things that almost never come up (unfortunately):
Half life calculaons
Types of Nuclear Fusion (magnec confinement, ineral confinement, cold fusion)
*In General, there are not many calculaon quesons from Nuclear Physics. It is mostly understanding and knowledge quesons. If you have a basic understanding of the
quesons you were assigned, and did well on the quizzes, you will be fine on this secon. And at the very least you will be able to make an educated guess if you are stumped*