1. Unit E, Chapter 3, Section 1, pE76-77
Energy
Unit E, Chapter 3, Section 1, pE76-77

2. Energy Energy Energy: ability to cause changes in matter
Objects, with energy can apply forces (push or pull)
Present around us in many forms
Electrical
Sound
Light
Mechanical, etc.
Changes from form to form
Electrical energy changes to light energy
Mechanical energy changes to thermal energy

3. Potential and Kinetic Energy
Kinetic energy: energy of motion
Can exert a force on matter in contact with it
Faster moving object = greater kinetic energy
Greater kinetic energy = greater force exerted
So …faster moving objects exert __?__ forces on objects
Potential energy: energy due to position (or condition) of an object
Takes energy to lift an object
Force of gravity pulling down
Energy is “stored” in the object
Greater

4. Potential and Kinetic Energy
Law of conservation of energy: the total amount of energy is a system is always the same – energy cannot be created or destroyed
Object lifted up:
Greater the elevation (height) = greater potential energy
More potential energy object has
More energy can be changed to kinetic energy
As an object drops:
Potential energy is changed to kinetic energy
Height decreases so potential energy decreases
Force of gravity causes the object’s speed to increase so kinetic energy increases

5. Potential and Kinetic Energy
As an object rises in the air:
Height increases so potential energy increases
Gravity causes the object’s speed to decrease so kinetic energy decreases
Kinetic energy is changed to potential energy
Law of conservation of energy
Ball stops rising
No kinetic energy
Greatest potential energy

6. Kinetic Energy Kinetic energy depends on the mass of objects
Bowling ball vs. tennis ball
Both traveling at 20 km/hr (12 mi/hr)
Which one will cause more changes to matter? Why?
Bowling Ball – It has more mass

7. Potential Energy Potential energy depends on the mass of objects
Energy cannot be created or destroyed
Moving objects with more mass = more kinetic energy
Objects with more mass (same height) = more potential energy

8. Potential and Kinetic Energy
Pendulum Investigation
What do these two diagrams show?