Notes about kinetic energy, potential energy and how calculate both.

1. Chapter 4
Section 1: The Nature of Energy
Thursday 10/31/13

2. Announcements
• Get homework ch 4 Reinforcement sec 1
from public folder
• Friday: GPE and KE calculations in class
• Labs on Monday and Wednesday
• Chapter 4 Test next Friday

3. What is energy?
• Every change that occurs involves energy
• Ex: throwing a baseball and breaking a
window, shifting position in your seat, writing
on paper, turning on a light
• Different forms of energy
– Electrical – using electricity
– Chemical – breaking chemical bonds
– Radiant – sun provides light energy for plants
– Thermal – sun provides heat energy

4. Kinetic Energy
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Definition: the energy of a moving object
Depends on an object’s mass and speed
Kinetic energy (KE) – unit in joules (J)
Mass (m) – unit in kilograms (kg)
Speed (v) – unit in meters per second (m/s)
KE = ½ m x v2

5. Potential Energy
• Energy can also be stored in a nonmoving object
– Ex: an apple hanging in a tree
• The energy stored has the potential to
cause change
– When the apple falls it could cause
a divot in the ground or leave a
bruise on someone’s head
• As it falls, the stored energy
(potential) is converted to energy of
motion (kinetic)

6. Types of Potential Energy
• Elastic Potential energy – stored energy
in something that can stretch or
compress
–Ex: rubber band or a spring
• Chemical Potential energy – stored
energy in chemical bonds
–Ex: food you eat and gasoline for cars

7. continued
• Gravitational Potential energy(GPE) – stored
energy by objects due to their height above
Earth’s surface
• Depends on the objects mass and height
• Gravitational potential energy (GPE) – joule (J)
• Mass (m) – unit in kilograms (kg)
• Gravity (g) – always use 9.8 m/s2
• Height (h) – unit in meters (m)
GPE = m x g x h

8. Homework
• Reinforcement Section 1 worksheet