work.notebook
January 19, 2017
Work
Work is only done when a force moves an object and part or all of the force must be parallel to the object's motion. Work is NOT done in the following situations:
• When there is motion, but no force Example: Voyager 2 satellite coasting in outer space
• When there is a force, but no motion Example: A pillar holding up a building
• When the force is perpendicular to the object's motion Example: ALL Uniform circular motion
Work = (Force)x(distance) Units of work: Newton­meter = Joule or J
Regents: W = Fd
since force and distance must be parallel AP:
W = FΔrcosθ
Dec 18­10:49 AM
Jan 19­8:10 AM
1
work.notebook
January 19, 2017
a. How much work is done in pulling up a 10 kg box at constant speed to a height of 5 meters?
b. How much work will be done to hold the box up at this height?
10 kg
Dec 18­11:00 AM
A 10 kg box is pushed 10 meters to the right with a force of 500 Newtons directed at 60 degrees. [a] How much work is done by the force?
60
10 kg
[b] If the box is moved at constant speed, how much work is done by friction?
[c] What is the net work done on the box?
Dec 18­11:08 AM
2
work.notebook
January 19, 2017
A 10 kg block is pulled at constant speed. How much work is done to pull the box up a hill that is 20 meters long?
10 k
g
30
Dec 18­11:14 AM
3