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Name:
Date:
Period:
Unit 1 Review Packet

List of vocabulary that you should know:
o Momentum
o Impulse
o ConSERvation of Momentum
o Collisions

Elastic Collision, Partially Inelastic Collision, Perfectly Inelastic Collision
o Explosion
o Mechanical Energies

Kinetic Energy, Potential Energy
o Work
o ConSERvation of Mechanical Energy
o ConSERvation of Energy versus ConVERsion of Energy
o Non-Mechanical Energies

Acoustic Energy, Chemical Energy, Electric Energy, Radiant Energy, Thermal Energy
o Alternative Energies

Wind, Hydroelectric, Solar (radiant to electricity AND thermal AND nuclear)
o Everyday Examples of Energy Conversion

Photosynthesis, Eating Food, Fuel for Car, Microphone, Toaster
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
Concepts that you should know:
o How does momentum change based on…

Mass?

Velocity?
o For impulse, how does force changed based on…

More time to impact?

Less time to impact?
o When should the Impulse-Momentum equation be used?
o If a green billiard ball is rolling to hit a yellow billiard ball that is at rest, where can
you see the following ideas in the situation…

Momentum?

Collision?

Impulse?
o How does the “Conservation of Momentum” equation for a(n)…

Elastic Collision demonstrate two objects bouncing apart?

Perfectly Inelastic Collision demonstrate two objects becoming one?

Partially Inelastic Collision demonstrate shape change or friction?

Explosion demonstrate one object becoming two?
o Which of Newton’s Laws is used to explain what happens to objects in an explosion?
o How do we indicate that two objects’ velocities are in OPPOSITE directions?

Left versus Right

Down versus Up

Backwards vs Forwards
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o Ideas about work…

Force must be ______________________________to displacement

If force is in the same direction as displacement…


Work must be ____________________, which will ____________________ the speed
If force is in the opposite direction as displacement…

Work must be ____________________, which will ____________________ the speed

If force is perpendicular to displacement, work must be __________

Given a problem, which of the three work equations should be used?

How are work and kinetic energy related?

How are work and gravitational potential energy related?
o Conservation of Mechanical Energy

In a pendulum (tennis ball on a string)

When does the tennis ball have all kinetic energy, potential energy, or both?
o In an elastic collision…

Is momentum conserved?

Is kinetic energy conserved?
o In a perfectly inelastic collision?

Is momentum conserved?

Is kinetic energy conserved?

What happens to the kinetic energy?
o When calculating power…

Which equation should you use to solve for work first? (Recall P = Work / Time)
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The following chart will also help you to determine which equations should be used for a specific problem. Based on things that you know in
the problem AND WHAT THE PROBLEM IS ASKING FOR, you should know when to use each equation.
Name of Equation
Momentum
Impulse
Impulse-Momentum
Theorem
Momentum in an
Elastic Collision
Equation
⃗ =m∙v
p
⃗
∆p
⃗ = ⃗F ∙ ∆t
⃗F ∙ ∆t = m ∙ ∆v
⃗

Easy: You know mass & velocity. Solve for momentum

Difficult: You know momentum & mass. Solve for velocity

Difficult: You know momentum & velocity. Solve for mass

Easy: You know force & time. Solve for impulse

Difficult: You know impulse & force. Solve for time

Difficult: You know impulse & time. Solve for force

Difficult: You know three of the four variables (Force, Time,
Mass, or Velocity) . Solve for the fourth variable

Solve for either a mass or a velocity

an explosion
Difficult: A perfectly inelastic (sticky) collision happens,
you know some masses & velocities,
mA v
⃗ A,initial + mB v
⃗ B,initial = (mA + mB )v
⃗ A&B,final
Collision
Momentum in
Difficult: An elastic (bouncy) collision happens,
you know some masses & velocities.
mA v
⃗ A,initial + mB v
⃗ B,initial = mA v
⃗ A,final + mB v
⃗ B,final
Momentum in a
Perfectly Inelastic
Use When…
Solve for either a mass or a velocity

(mA + mB )v
⃗ A&B,initial = mA v
⃗ A,final + mB v
⃗ B,final
Difficult: An explosion (separation) happens,
you know some masses & velocities. Solve for either a mass or a
velocity
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Name of Equation
Equation
Kinetic Energy
1
KE = mv 2
2
Potential Energy
PE = mgh
Work
Work – KE Theorem
W=F∙d
W=
1
1
2
2
mv
⃗ f − mv
⃗i
2
2
Use When…

Easy: You know mass & velocity. Solve for KE

Medium: You know KE & velocity. Solve for mass

Difficult: You know KE & mass. Solve for velocity

Easy: You know mass, gravity, & height. Solve for PE

Medium: You know PE, mass, & gravity. Solve for height

Medium: You know PE, gravity, & height. Solve for mass

Easy: You know force & displacement. Solve for work

Medium: You know work & force. Solve for displacement

Medium: You know work & displacement. Solve for force

Medium: You know mass & velocities. Solve for work
Work – PE Equation
W = −(mghfinal − mghinitial )

Medium: You know mass, gravity, & heights. Solve for work
Conservation of
1
1
ghinitial + vi 2 = ghfinal + vf 2
2
2

Hard: You know gravity, some heights, & some velocities.
Mechanical Energy
Power
P=
Work
Time
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Solve for either a height or a velocity

Medium: You know work (which can be calculated) and time.
Solve for power
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The following problems give examples related to the previous chart.
1. Momentum – Easy
If a 2kg object is moving at 4m/s, what is its momentum?
2. Momentum – Difficult
If a 2kg object has a momentum of 10kg*m/s, what is its velocity?
3. Momentum – Difficult
If an object has a momentum of 15kg*m/s and is moving at 3m/s, what is its mass?
4. Impulse – Easy
You impact a wall with a force of 2N. It takes 3s to complete the impact. What is your impulse?
5. Impulse – Difficult
You run into a wall and have an impulse of 16 kg*m/s. If you feel 4N of force, how long did it take
to complete the impact?
6. Impulse – Difficult
You run into a wall and have an impulse of 16 kg*m/s. If you take 2s to complete the impact, what
force do you feel?
7. Impulse-Momentum Theorem – Difficult
An airbag stops you in a collision in 2 seconds. You are 55kg heavy and you were driving at
20m/s. What is the force you will feel?
8. Momentum in an Elastic Collision – Difficult
A 12kg billiard ball rolls to the right at 1m/s and hits a 4kg billiard ball that is at rest. They
bounce off without deforming. After the collision, the 12kg billiard ball continues to move to the
right at 0.5m/s. What is the 4kg billiard ball’s final velocity AFTER collision?
9. Momentum in a Perfectly Inelastic Collision – Difficult
A 12kg clay ball rolls to the right at 1m/s to hit and stick to a 4kg clay ball that is at rest. What is
the velocity of the combined clay ball AFTER collision?
10. Momentum in an Explosion – Difficult
A 1.5kg cannon is loaded with a 0.06kg ball (total mass is 1.56kg). The apparatus is at rest. The
cannon is ignited and launches the 0.06kg ball forward at 75m/s. What is the velocity of the cart
following the explosion?
11. Kinetic Energy – Easy
What is the kinetic energy of a 6kg box moving at 7m/s?
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12. Kinetic Energy – Medium
A box has 16J of kinetic energy and is moving at 2 m/s. What is its mass?
13. Kinetic Energy – Difficult
A 7kg box has 28J of kinetic energy. What is its velocity?
14. Potential Energy – Easy
An 80kg man is standing on the edge of a table 2m above the ground. What is his gravitational
potential energy? (Recall: g = 10m/s2)
15. Potential Energy – Medium
A 2kg object has 200J of gravitational potential energy. How high is the object?
(Recall: g = 10m/s2)
16. Potential Energy – Medium
An object has 400J of gravitational potential energy and is 5 m high. What is the object’s mass?
(Recall: g = 10m/s2)
17. Work – Easy
An object is pushed with a force of 20N, which causes a 3m displacement. What is the work done?
18. Work – Medium
An object has 15J of work done on it by a 3N force. What is its displacement?
19. Work – Medium
An object has 21J of work done on it and is displaced 7m. What was the force working on it?
20. Work-KE Theorem – Medium
What is the work done on a 5kg box that goes from 10m/s to 4m/s? Is the work done positive or
negative? Why?
21. Work-PE Equation – Medium
What is the work due to gravity done on a 2kg rock that goes from 15m high toe 6m high? Is the
work done positive or negative? Why?
22. Conservation of Energy – Hard
A cow is at rest at 8m high and then is dropped. What is its velocity when it is still 2m above the
ground?
23. Power – Medium  This is calculated using work solved with the Work-PE Equation!
A 20kg cylinder in a clock falls from 1.5m high to 0.5m high in 300,000s. What is the clock’s
power? (Recall: g = 10m/s2)
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Momentum and Impulse
Work, Energy, and Power
Momentum
Kinetic Energy
⃗ =m∙v
p
⃗
1
KE = mv 2
2
Impulse
Potential Energy
∆p
⃗ = ⃗F ∙ ∆t
PE = mgh
**Recall that g = 10 m/s2
Impulse-Momentum Theorem
⃗F ∙ ∆t = m ∙ ∆v
⃗
Work Equations
1. W = F ∙ d
Conservation of Momentum
1
2
1
2. W = mv
⃗ f − mv
⃗i
2
⃗ initial = p
p
⃗ final
2
2
3. W = −(mghfinal − mghinitial )
Momentum in an Elastic Collision
mA v
⃗ A,initial + mB v
⃗ B,initial = mA v
⃗ A,final + mB v
⃗ B,final
Conservation of Mechanical Energy
1
1
ghinitial + vi 2 = ghfinal + vf 2
2
2
Momentum in a Perfectly Inelastic Collision
mA v
⃗ A,initial + mB v
⃗ B,initial = (mA + mB )v
⃗ A&B,final
Power
P=
Momentum in an Explosion
Work
Time
(mA + mB )v
⃗ A&B,initial = mA v
⃗ A,final + mB v
⃗ B,final
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Measurement
Equation
Symbol
Mass
m
Velocity
⃗
v
Momentum
⃗
p
kg ∙ m⁄
s
(kilogram-meters per second)
Impulse
∆p
⃗
kg ∙ m⁄
s
(kilogram-meters per second)
Force
⃗F
N
(Newtons)
Time
t
s
(seconds)
Displacement
⃗d
m
Work
W
J
(Joules)
Kinetic Energy
KE
J
(Joules)
Potential Energy
PE
J
(Joules)
Height
h
m
(meters)
Gravity
g
10 m/s2 (meters per second squared)
Power
P
Watts
Units Used With Numbers
kg
m⁄
s
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(kilograms)
(meters per second)
(meters)
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