2. 6.1 Work
Work is done when a force is applied to an object and the object moves in the direction of the applied force.

3. Work is measured with a unit called the joule.
Example:
Work is measured with a unit called the joule.
p. 191
3.) 25 J
Work is zero if the distance moved is zero.
W = Fd
W = F x 0 = 0
The boy is holding the weights, which don't move. No work is being done, so why does he get tired?
The individual cells in his muscles are contracting and relaxing as he holds the weights. The muscles cells are doing work, but no work is done on the weights because they are at rest the whole time.

4. The angle of the force affects the work done.
p. 193
5.) 0.17 kJ

5. Work can be positive, negative, or zero.
(when 0 = 90o)
W = -Fd
(when 0 = 180o)
p. 194
B<A<C<D

6. The work done by separate forces can be summed.
Wtotal = W1 + W2 + W3+...
p.196
8.) W = Fd
9.) Use the component of the force in the direction of the displacement.
10.) No, the displacement will be zero.
11. a) not possible
b.) work done when sliding book is brought to rest by friction

7. 6.2 Work and Energy Kinetic Energy
The energy of motion depends on mass and speed.
Doing work on an object changes its speed.

8. Work and kinetic energy are related.
p. 199
16.) 0.47 J
17.) 1200 kg
18.) 32 m/s
Work and kinetic energy are related.
p.201
20. a) 7.2 J
b) 11 m/s
c) 18 J
p. 201

9. Potential Energy: stored energy.
Two types:
Gravitational
Elastic
Potential energy, like all energy, is measured in joules (J), the same unit used for work.
p. 206
27.) doubles, triples
28.) increase, positive work increases kinetic energy
29.) negative, the work is negative because the change in KE is negative
30.) no, because the weight of the box is different in each case.
31.) increases by a factor of 4