Potential Energy (B)
Definitions of Energy
Potential Energy
Potential energy describes the potential (stored) energy of an object. The amount of stored energy
depends on the object’s position. In other words, we can think of potential energy as the stored
energy of position.
One type of potential energy is called gravitational potential energy. Gravitational potential energy
depends on the object’s height from the ground (often measured in meters), the pull of gravity
(measured in meters per second squared), and the mass of the object (measured in kilograms).
The formulas used to represent potential energy include the following:
PEgrav = m x h x g
PEgrav = m  h  g
PEgrav = mhg
All three formulas above represent the same thing: to obtain an object’s gravitational potential
energy, you multiply mass by height by the force of gravity. The amount of potential energy an
object has is expressed in the energy unit known as the joule (J). Note: 1 joule = 1 kg x (m/s) 2.
1. Based on the information given above, what does each variable in this formula represent, and
what unit goes with each variable?
Variable
Meaning
Unit
m
h
g
2. An Olympian lifts a 1375 kilogram set of weights a vertical distance of 2.0 meters in the weight
lifting event. The force of gravity equals 9.8 m/s2. What is the potential energy of the weights?
PE =
m
x
h
x
g
3. A child wants to reach the cookies on the top shelf of the kitchen. The shelf is 1.5 m high. The
cookie jar has a mass of 0.75 kg. What is the potential energy of the cookie jar before it is taken
from the shelf? Round your answer to the nearest hundredth.
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Potential Energy (B)
Definitions of Energy
4. 6.0 J of work is done to raise a 0.48-kg box from a shelf. How far was the box lifted from the
shelf? Round your answer to the nearest tenth.
a.Rearrange the formula to solve for height.
b.Use the formula to solve for the height of the lift.
5. A 15-kg cart filled with apples is sitting at the top of a hill that is 21 m high. The apples in the
cart have a mass of 33 kg. What is the potential energy of the cart and the apples? Round your
answer to the nearest whole number.
6. A weight training ball is put on a ledge 3.0 m high. The potential energy of the ball on the ledge
is 200 J. What is the mass of the ball? Round your answer to the nearest tenth.
a.Rearrange the formula to solve for mass.
b.Use the formula to solve for the mass of the ball.
7. A small, private airplane is carrying three passengers to an island. The plane is 0.9 km in the
air. If the potential energy of the plane and its three passengers is 48,510,000 J, what is the
combined mass of the plane and its passengers? Round your answer to the tenth place.
a.Convert the height in km to m.
b.Rearrange the formula to solve for mass.
c.Use the formula to solve for the mass of the plane and passengers.
8. If the plane from question 7 has a mass of 5275 kg, and all three passengers have the same
mass, what is the mass of each passenger?
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