1. Energy

2. Energy Forms Energy: The capacity for doing work.
It exist in various forms such as thermal, electrical, chemical, nuclear, or other various forms.
We will be looking at energy in the process of transferring from one body to another

3. Kinetic Energy Kinetic Energy – energy that has motion
kinetic energy depends upon an object’s mass and velocity.
Doing work on an object can increase the kinetic energy.
Formula:
KE= ½ m v2
KE= joules
M=mass
V=velocity

4. Questions about Energy
1. What happens to the KE of an object when: a) mass is doubled b) velocity is doubled c) velocity is halved

5. Example
2. What is the kinetic energy of a 1kg block that is moving with a velocity of 2 m/s?

6. Potential Energy
Gravitational Potential Energy – stored energy because of its state or position.
Energy that depends upon the objects position above the earth’s surface.
PE= mgh
M= mass-kg
G=gravitational acceleration-m/s2
H= height-m

7. Questions about Energy
1. An object is being lifted up. Is the object’s GPE increasing or decreasing?

8. Example
What is the gravitational potential energy of a 2 kg object that is raised to height of 10 m?

9. Questions about Energy
3. A rock is falling down. As it is falling down, what is happening to its GPE? As it is falling down, what is happening to its KE?

10. Energy Forms
Mechanical Energy: The total kinetic and potential energy for an object (or multiple objects)

11. Work, Energy Theorem
The work- energy theorem states that the change in the kinetic energy of an object is equal to the net work done in/to it.
Net Work = ½ mvf^2 – ½ mvi^2

12. Conservation of Energy
Law of Conservation of Energy:
Within a closed, isolated system, energy can change form, but the total amount of energy is constant. Energy can not be created or destroyed. Ex. Kinetic to Potential Energy

13. Conservation of Mechanical Energy
Mechanical energy is always conserved in a closed system (no friction)
a decrease in potential energy is accompanied by an increase in kinetic energy.
Formula: KEi + PEi = KEf + PEf

14. Problem
A large chunk of ice with a mass of 15 kg falls from a roof 8m above the ground. Find the KE of the ice when it reaches the ground. What is the speed of the ice when it reaches the ground?
KE + PE (initial) = KE + PE (final)