1. Chapter 7
Energy

2. Work = Force|| x Distance
In this case, the distance is the magnitude of the displacement.
Only the component of force parallel or antiparallel to the displacement does work

3. M= 10kg
In this case, the weight does positive work
d = 2 m
Work = Mgd = (100N)(2m)
Work = 200 Nm =200J
M= 10kg
Mg = 100N

4. Fa Fa M= 10kg In this case, the weight does negative work Mg = 100N
d = 2 m Fa
Work = -Mgd = -(100N)(2m)
Work = -200 Nm = -200J
M= 10kg
Mg = 100N

5. Potential Energy
An object’s ability to do work by virtue of its position.

6. How much work does gravity do on the falling mass?
PE = mgh mg h h
Work = mgh mg

7. How much energy does the mass have at the bottom just before it hits the ground?
PE = mgh mg h h
Work = mgh mg v

8. How much energy does the mass have at the bottom just before it hits the ground?
This is the kinetic energy
PE = mgh mg h
KE = ½ mv2
Work = mgh mg v

9. Energy is conserved

10. PE = 1000J
KE = 0J
PE = 800J
KE = 200J
PE = 400J
KE = 600J
PE = 0J
KE = 1000J

11. PE = 500J
KE = 0J
PE = 100J
PE = 100J
KE = 400J
PE = 0J
KE = 400J
KE = 500J

12. Machines N M D F d Mg
Fulcrum
Work = FD = Nd