Physics Phynal Exam REVIEW
Rawding Period 8 – ORANGE
Topics covered on exam
A.
B.
C.
D.
E.
F.
G.
Uniform Circular Motion
Gravitation
Impulse and Momentum
Torque and Rotation
Waves and Sound
Refraction and Lenses
Electric Current and Circuits
All of the mathematical models for the exam will be provided for you.
A.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Circular motion and centripetal force
Centripetal acceleration always occurs towards the center of the circle
Centripetal force always acts towards the center of the circle.
Forces that can act as the centripetal force include tension, friction and gravitation
The tangential velocity of an object in circular motion is perpendicular to the centripetal force
The factors affecting the force needed to keep an object in uniform circular motion are mass, radius and
tangential velocity
If the centripetal force stops acting on the object, the object will move in a straight line because of its
inertia.
Uniform circular motion is motion with a constant speed but not a constant velocity because velocity
includes direction.
The period of an object moving around in a circle is the time for one complete movement around a circle.
The distance traveled around a circle is the circumference
C=2··r
10. The tangential velocity can be calculated using radius and period of body in uniform circular motion of
radius, r, and period, T.
vT =
2·  ·r
T
11. The centripetal acceleration of an object traveling in uniform circular motion at tangential velocity, v, in a
circle of radius, r is calculated using this mathematical model.
v2
ac 
r
12. The centripetal force needed to hold various bodies in uniform circular motion is using this mathematical
model.
13. Rotational velocity is the number of turns in a given time. A spinning object has the same rotational
velocity everywhere on the spinning object.
B. Gravitational Attraction, Kepler’s Laws and Satellites
1. A gravitational attraction exists between every pair of masses in the universe, large or small
2. Mass influences the force of gravity between two bodies. The more massive the body
the larger the gravitational force. The force is proportional to the product of the two
masses.
FG  mA  mB
3. The gravitational attraction between two masses is inversely proportional to the square of
the distance between the two masses. When the distance between two masses is doubled,
the force of attraction between the masses will decrease by 1/4th
FG 
1
r2
4. “little” g is a value that describes the gravitational field strength at a given location. “little” g changes from
planet to planet. “little” g is 9.8 m/s2 on Earth.
5. The universal gravitational constant measured by Cavendish, BIG “G” is the same everywhere in the
universe.
N · m2
G  6.67 x10 -11
kg 2
6. To calculate the gravitational force acting between two masses use Newton’s Law of
Universal Gravitational Attraction.
FG  G ·
mA · mB
r2
7. The acceleration due to gravity, g, on a planet depends on the mass and radius of the planet. A very
massive planet with a small radius will have a large value for g.
8. The gravitational field around the Earth points inward towards the center of the Earth
9. Kepler’s Three Laws for orbiting systems like our solar system state that the planets
orbit the sun in elliptical shaped orbits K1L, the planets sweep out equal areas in
equal units of time, K2L, and that the ratio of the period squared of two planets is
equal to the ratio of the orbital radius cubed, K3L
2
 TA   rA 
    
 TB   rB 
3
10.
The sun is located at one of the foci in the elliptical orbit of the planet.
11.
12.
Circular orbits have the same velocity, potential energy, and kinetic energy everywhere in the orbit.
Elliptical orbits have most velocity and kinetic energy when the planet is closest to the sun.
13.
Einstein’s view of gravitation is that gravitation is a distortion of the fabric of space-time
C. Momentum and Impulse
1. All moving objects have momentum. Momentum can be calculated using.
2. Calculate the change in momentum of an object.
3. Relate force and time to change in momentum.
4. Impulse is the force acting on an object times the
making contact with the object.
p  mv
p  p f  pi
Ft  impulse
time that the force is
5. A large applied force can act for a small amount of time and create the same impulse as a small applied
force acting for a large amount of time.
6. An impulse causes a change in the momentum of an object.
p  Ft  impulse
7. The mathematical model for the impulse – momentum theorem, to find unknown quantities.
pi  Ft  p f
mvi  Ft  mv f
8. The interaction between two objects in a collision follow Newton’s third law (equal and opposite forces).
FAonB  FBonA
t AonB  tBonA
Ft AonB  Ft BonA
9. The law of the conservation of momentum states that the total momentum before a collision is equal to the
total momentum after the collision.
p
i
  pf
provided  F  0 N
10. The unknown quantity of mass or velocity in conservation of
momentum problems, elastic, inelastic and perfectly inelastic collisions (and explosions).
m1v1i   m2v2i   m1v1 f   m2v2 f 
m1v1i   m2 v2 i   m1  m2 v f
m1  m2 vi  m1v1 f   m2v2 f 
D. Torque, Center of Gravity and Rotational Equilibrium
1. Torque is calculated using the mathematical model.
  Fr
2. The units for torque are Nm.
3. An unbalanced torque acting on an object will cause a change in the rotation of the object. It may be
caused to start rotating, stop rotating or change the rate of rotation.
4. The distance used to calculate torque is always measured from the pivot point to the place where the force
is applied.
5. A force applied right at the pivot point will not create a torque.
6. A force applied parallel to the lever arm will not create a torque.
7. Rotational equilibrium occurs when the sum of the clockwise torques equals the sum of the counter
clockwise torques.
8. Forces can either create a clockwise torque or a counterclockwise torque.
9. The center of gravity of a symmetrical uniform density object is in the geometric center.
10. The center of gravity of an object will hang directly below the point of suspension of an object.
11. The center of mass of an object will follow a straight line path when the object is spun along the ground.
The center of mass of an object will follow a smooth parabolic path when an object is thrown through the
air.
12. An object will not topple if the center of gravity of the object is in a line directly above or directly below the
supporting base of the object.
13. When the weight vector, drawn from the center of gravity of the object, does not pass through the
supporting base of the object, the object will topple.
14. The Law of the Conservation of Angular Momentum states that the angular momentum of a spinning object
will be conserved provided no external torque acts on the object.
15. Angular momentum is calculated by multiplying rotational inertia of the object with the rate of spin.
16. The rotational inertia of an object depends on the distribution of themass of the object, the mass and the
radius of the object.
17. A figure skater can change his rotational inertia by extending his arms or legs outward or pulling them in
tight to his body. Weight far away from the axis of rotation will create a large rotational inertia.
18. Conservation of angular momentum of a figure skater; A figure skater spinning at a slow rate with his arms
and leg out away from his body can bring his arms and legs in tight to his body thus causing his rotational
inertia to decrease and therefore his rate of spin will increase.
E. Wave Behaviors and Sound
1. Energy is transferred when a wave travels through a medium
2. A longitudinal wave has particles on the wave that move parallel to the direction of motion of the wave. A
pressure wave or a sound wave are longitudinal waves.
3. A transverse wave has particles on the wave that move perpendicular to the direction of motion of the
wave. Electromagnetic radiation is a transverse wave.
4. Wave velocity can be calculated in terms of its frequency and wavelength,
v
wavelength
v  f
, or period and

T ,
5. The speed of a sound wave can be determined by timing an echo. If sound is sent a distance and timed to
travel that distance, the speed of sound can be calculated using distance traveled divided by the time.
6. Constructive interference occurs when two crests line up and the amplitude of the two crests add together
to create a larger wave.
7. Destructive interference occurs when a crest lines up with a trough causing the resulting amplitude to be a
smaller wave.
8. The principle of superposition states that when two pulses occupy the same space, their amplitudes will
combine to create a new pulse with an amplitude equal to the sum of the original two amplitudes. The sign
of the amplitude is important.
9. Resonance occurs when the natural vibrational frequency is matched by the forced vibrational frequency.
The amplitude of vibration will increase when resonance occurs. Resonance occurred in the singing pipes
lab and also in the collapse of the Tacoma Narrows Bridge.
10. A standing wave forms when two identical waves, traveling in opposite directions, interfere with each other.
The standing wave appears to be standing still. The standing wave is made up of alternating regions of no
motion called nodes, and regions of maximum displacement called antinodes.
11. The frequency range of human hearing is between 20 Hz to 20000 Hz.
12. Ultrasonic waves are greater than 20000 Hz, and infrasonic sound waves are less than 20 Hz.
13. Diffraction of a wave occurs around an obstacle or through an opening. The wave bends around the
obstacle without any change in medium. Huygen’s wavelet theory provides a model for explaining the
bending of light around an obstacle.
14. An interference pattern forms when two point sources of waves oscillate at the same frequency in the same
space. The interference pattern is alternating regions of constructive and destructive interference. For red
laser light, an interference pattern created through a diffraction grating will produce a row of red bright
spots.
15. Some real life examples of values on the decibel scale. From physicsclassroom.com
0 decibels
quietest sound humans can
hear, threshold of hearing
20 dB
whisper
60 dB
normal conversation
80 dB
Vacuum cleaner
110 dB
front row of a rock concert
130 dB
threshold of pain
16. The Doppler Effect is a shift in the observed frequency of a sound as the source of the sound or the
observer of the sound moves.
Source of sound
Source of sound
Observer moving
Observer moving
moving TOWARDS
MOVING AWAY
TOWARDS source
AWAY FROM
observer
from observer
of sound
source of sound
Perceived HIGHER
Perceived LOWER
Perceived HIGHER
Perceived LOWER
frequency (pitch)
frequency (pitch)
frequency (pitch)
frequency (pitch)
sound
sound
sound
sound
F. Light Refraction and Lenses
1. A real image can be projected on a screen because light rays actually converge to form the image. Real
images are always inverted.
2. A virtual image cannot be projected on a screen. Virtual images are upright. A plane mirror forms a virtual
image. A converging lens when used as a magnifying glass produces a virtual image.
3. The lens/mirror equation can be used to solve for the focal length of a lens, f , given the
object distance and the image distance.
1 1 1
 
f di do
4. The magnification of an image is calculated using the ratio of the height of the image to
the height of the object.
m
hi
d
 i
ho
do
5. The speed of light in a medium is related to the index of refraction of light in a new medium
nx 
c
vx
6. Refraction occurs when light passes from one medium into another medium. The angle of refraction is
measured between the refracted ray (transmitted into the new medium) and the normal line. When light
enters a slower medium, the refraction angle will be smaller than the angle of incidence. Light will be bent
towards the normal when it enters a slower medium.
7. The index of refraction of the medium relates to the speed of light in the medium. A large index of
refraction indicates that the speed of light in the new medium is slower. A medium with a large index of
refraction will cause the light to be bent more towards the normal.
Snell’s law of refraction can be used to predict the path of light as it travels from one medium to another
based on the index of refraction of the medium.
n1 sin 1  n2 sin 2
8. Images formed by a converging lens can be described based on where they are located, their relative size
and their orientation depending on where the object is placed. is beyond 2f, at 2f, between f and 2f and
inside f.
Object Location
Image
Smaller, same
Upright or inverted Real or virtual
Location
size, larger
Beyond 2f
Between f and 2f
Small
Inverted
Real
At 2f
Same
Inverted
Real
Beyond 2f
larger
Inverted
Real
Upright
Virtual
At 2f
Between 2f and f
At f
Between f and the
mirror/lens
NO IMAGE
Same side of lens
as object
larger
G. ELECTRIC CIRCUITS
1. Electric current is the rate of flow of charge.
2. An electrical circuit is a closed loop path through which current can flow. The components of a circuit are
the source of potential difference (the battery), the conducting wires, and a load (light bulb or resistor).
3. Conventional current flows in the direction positive charges would move. Conventional current flows out of
the positive terminal of the battery and into the negative terminal.
4. Electric current (I) is measured in amperes (A), or amps, and can be calculated by finding
the total amount of charge ( q), in Coulombs, which passes a specific point in a given time
(t).
5. A battery is a device that converts chemical energy into electric energy. The battery is the source of
potential difference V.
6. Voltage, also known as, potential difference is the energy given per charge.
7. Ohm's Law states that the resistance opposes current flow so the higher the equivalent
resistance in a circuit, the lower the current flow. The resistance is inversely proportional
to the current flow.
V
I
8. Ohm’s Law also states that the potential difference promotes current flow so the larger the potential
difference provided the larger the current flow. The voltage is directly proportional to the current flow.
9. Ohm's Law may be used for the entire circuit or for any individual resistor in the circuit.
R
10. Voltmeters are tools used to measure the potential difference, voltage, between two points in a circuit.
Voltmeters are wired in parallel (because voltage is the same in parallel). Potential difference is measured
in Volts.
11. Ammeters are tools used to measure the current in a circuit. The ammeter is connected in series with the
circuit. (because current is the same in series). Current is measured in Amperes
12. The Junction rule (aka current Rule) for parallel circuit states that the sum of all
the currents entering a junction equals the sum of all the currents leaving the
junction. This rule is based on the conservation of electric charge.
I1  I 2  I 3
13. Voltage (Loop) Rule: The voltage gained through the battery must equal the sum of all of the voltage
drops around the circuit. This rule is based on the law of conservation of energy
14. Electrical power is the rate at which electrical energy is expended. The total power
provided by the battery always equals the sum of the power used by each of the individual
resistors no matter how the resistors are connected in the circuit.
15. Conservation of energy applies to electrical circuits, so the energy used in the resistor is converted into
heat (in most cases) and light
Resistors in Series
16. There is only a single current path in the circuit, which travels through all resistors in series.
All resistors in series have equal current. Adding a resistor in series increases the total resistance of a circuit.
An increase in total resistance will cause a decrease in current flow.
The following rules apply to a series circuit:
 The sum of the potential drops equals the potential rise of the source.
 The current is the same everywhere in the series circuit.
 The total resistance of the circuit (also called effective or equivalent resistance) is equal to the sum of
the individual resistances.
Resistors in Parallel
17. All resistors in parallel have equal voltage. Adding a resistor in parallel decreases the total resistance of a
circuit. Parallel circuits provide multiple current paths.
The following rules apply to a parallel circuit:
 The potential drops of each branch equals the potential rise of the source.
 The total current is equal to the sum of the currents in the branches.
 The inverse of the total resistance of the circuit (also called effective or equivalent resistance) is
equal to the sum of the inverses of the individual resistances.
One important thing to notice from this last equation is that the more branches you add to a parallel
circuit (the more things you plug in) the lower the total resistance becomes. Remember that as the total
resistance decreases, the total current increases. So, the more things you plug in, the more current has
to flow through the wiring in the wall. That's why plugging too many things in to one electrical outlet can
create a real fire hazard.