PS8 Motion Day 4

Name: ________________________________________________ Date: ______________ Period: ________
Unit 5: Motion (Day 4 – Energy)
Warm Up:
In which interval do you think the roller coaster cart has the most energy? Explain your answer.
Notes:
Section 9.4: Energy
Energy is ________________________________________.
___________ is done when an object is caused to move a certain distance.
The _______ unit for both energy and work is the ___________________.
Kinetic Energy
________________ is energy due to motion. It depends on ___________ and _________.
The formula for kinetic energy is:
Example 1: What is the kinetic energy of a jogger with a mass of 65.0 kg traveling at a speed of 2.5 m/s?
G
U
givens
E
unknowns
equations
S
S
substitute
solve
Example 2: What is the mass of a baseball that has a kinetic energy of 105 J and is traveling at 10 m/s?
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givens
U
unknowns
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equations
S
S
substitute
solve
Example 3: What is the kinetic energy of a 0.38 kg soccer ball that is traveling at a speed of 120 m/s?
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givens
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unknowns
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equations
S
S
substitute
solve
Example 4: What is the kinetic energy of a 0.50 kg ball travelling at a speed of 120 m/s?
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givens
U
unknowns
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equations
S
S
substitute
solve
Example 5: What is the kinetic energy of a 0.50 kg ball that is travelling at a speed of 40 m/s?
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givens
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unknowns
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equations
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substitute
solve
Potential Energy
________________ is energy due to position. There are two types of potential energy.
_______________________________________(GPE) is energy due to the _________________ for
_______________ to set an object in motion. It depends on ______________ and ________________.
Weight is a _____________ that is equal to an object’s __________ multiplied by _____________________
___________________. The formula for GPE is:
Because gravitational potential energy depends on ___________, and weight depends on ____________,
GPE depends on_____________.
Example 1: Does an object held 3 m above the surface of the moon have the same GPE as the same
object held 3 m above the surface of the earth? Explain your answer.
Example 2: Find the gravitational potential energy of a light that has a mass of 13.0 kg and is 4.8 m above
the ground.
Example 3: An apple in a tree has a gravitational potential energy of 175 J and a mass of 0.36 kg. How high
from the ground is the apple?
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givens
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unknowns
equations
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substitute
solve
Example 4: A marble is on a table 2.4 m above the ground. What is the mass of the marble if it has a
gravitational potential energy of 5.68 J?
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U
givens
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unknowns
equations
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substitute
solve
Example 5: A box with a mass of 12.5 kg sits on the floor. How high would you need to lift it for it to have
a GPE of 355 J?
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givens
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unknowns
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equations
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substitute
solve
Example 6: A cart at the top of a 300 m hill has a mass of 40,000 g. What is the cart’s gravitational
potential energy?
_____________________(EPE) is the potential to move because of being stretched or squeezed.
Law of Conservation of Energy
The Law of Conservation of Energy states that _________________________________________________
_______________________________________________________________________________________.
________________________ and ______________________ are two forms of energy.
Whenever an object rises or falls some of its energy changes from being ____________ to kinetic or changes
from being _____________ to being potential.
Lab: Energy Investigation Lab
Materials: Newton’s Cradle, metal ball, ping-pong ball, ruler, spring-loaded pen, plastic spoon, spinning top
1. Pull one of the spheres on the end of the Newton’s Cradle back. Don’t let go. Is most of its energy
potential or kinetic? Explain.
2. Release the sphere. As it moves toward the other spheres is most of its energy potential or kinetic?
Explain.
3. What law explains why other spheres start moving when the first sphere stops moving? Explain your
answer.
4. What two factors affect gravitational potential energy?
5. Drop the wood or metal ball from 10 cm above the table. Then drop the ping-pong ball from the same
height. Do they have the same amount of potential energy before you drop them? Explain.
6. Now drop the metal ball from 30 cm above the table. Does it have the same amount of potential energy
as when you dropped it from 10 cm above the table? Explain.
7. Push on the end of the pen. What type of potential energy does it have before you let go?
8. Pull back on the spoon as if you were about to start a food fight (but don’t start a food fight!). What type
of potential energy does the spoon have before you let go?
9. Spin the top. What form is most of its energy when it is spinning? Eventually it stops spinning. What
happened to the energy? Was it destroyed?
Cool Down:
Title: Kinetic and Potential Energy Double Bubble Map
Homework:
Vocabulary
Word
work
energy
kinetic
energy
potential
energy
gravitational
potential
energy
Textbook Definition
Example in a Sentence
(Underline the Word)
elastic
potential
energy
Law of
Conservation
of Energy
1. What unit is used to measure energy?
2. What factors affect an object’s kinetic energy?
3. A 1,500 kg cart is moving at a speed of 10 m/s. What is the car’s kinetic energy?
4. What factors affect an object’s gravitational potential energy?
5. What is the potential energy of a 100 kg pole-vaulter when she is 4 m above the ground?
6. State the Law of Conservation of Energy in your own words.
7.
Suppose a ball with a mass of 0.2 kg was held at a height of 2 m above the ground.
a. What is its potential energy?
b. What would its kinetic energy be as it hit the ground?
c. What would its velocity be as it hit the ground?

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