1. Physical Science Chapter 13 Section 3
What is Energy?
Physical Science
Chapter 13
Section 3

2. Energy and Work
When work is done, energy is transformed or transferred.
Energy exists in an object whether or not it is moving

3. Potential Energy
Results from the relative positions of objects in a system.
It can exist as elastic potential energy if an object is stretched or gravitational potential energy depending on the distance from the ground.

4. Potential Energy Gravitational Potential Energy Equation: PE = mgh
PE = gravitational potential energy (J)
M = mass (kg)
G = free-fall acceleration (9.8 m/s2 on Earth)
H = height (m)

5. Potential Energy
A 65 kg rock climber ascends a cliff. What is the climber’s gravitational potential energy at 35 m above the base of the cliff?
Mass, m = 65 kg
Height, h = 35 m
Free-fall acceleration, g = 9.8 m/s2
Gravitational potential energy, PE = ? J
PE = (65 kg)(9.8 m/s2)(35 m) = J

6. Potential Energy
What is the gravitational potential energy of a 1200 kg car at the top of a hill the is 42 m high?

7. Potential Energy
What is the gravitational potential energy of a 65 kg climber on top of Mt. Everest (8800 m high)?

8. Potential Energy
What is the gravitational potential energy of a 0.52 kg bird flying at an altitude of 550 m?

9. Potential Energy
A student holds a kg egg out a window. The egg has 8 J of gravitational potential energy. How high is the egg in meters?

10. Potential Energy
A diver has 3400 J of gravitational potential energy after climbing up onto a diving platform that is 6 m above the water. What is the diver’s mass in kilograms?

11. Kinetic Energy Depends on both mass and speed.
If an object is not in motion it does not have kinetic energy.
Kinetic Energy Equation:
Kinetic energy = ½ x mass x speed squared
KE = ½mv2

12. Kinetic Energy
What is the kinetic energy of a 44 kg cheetah running at 31 m/s2?
Mass, m = 44 kg
Speed, v = 31 m/s2
Kinetic energy, KE = ? J
KE = ½mv2
KE = ½(44)(31)2 = J

13. Kinetic Energy
Calculate the kinetic energy of a 1500 kg car that is moving at a speed of 12 m/s.

14. Kinetic Energy
A 35 kg child has 190 J of kinetic energy after he sleds down a hill. What is the speed of the child?

15. Kinetic Energy
A bowling ball traveling 2 m/s has 16 J of kinetic energy. What is the mass of the bowling ball in kilograms?

16. Other Forms of Energy
Mechanical energy is the amount of work that an object can do because of it’s kinetic and potential energies.
Nonmechanical energy occurs on the level of atoms.