work

work force and distance

Work is directly related to both the force applied to an object and the distance the object moves. It can be represented by the equation: Work = Force Distance This equation shows that the greater the force that is used to move an object or the farther the object is moved, the more work that is done. To see the effects of force and distance on work, compare the weight lifters in the Figure 1.2. The two weight lifters on the left are lifting the same amount of weight, but the one on the bottom is lifting the weight a greater distance. Therefore, this weight lifter is doing more work. The two weight lifters on the bottom right are both lifting the weight the same distance, but the weight lifter on the left is lifting a heavier weight, so she is doing more work.

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defining work

Work is defined differently in physics than in everyday language. In physics, work means the use of force to move an object. The teens who are playing basketball in the picture above are using force to move their bodies and the basketball, so they are doing work. The teen who is studying isnt moving anything, so she isnt doing work. Not all force that is used to move an object does work. For work to be done, the force must be applied in the same direction that the object moves. If a force is applied in a different direction than the object moves, no work is done. The Figure 1.1 illustrates this point. Q: If the box the man is carrying is very heavy, does he do any work as he walks across the room with it? A: Regardless of the weight of the box, the man does no work on it as he holds it while walking across the room. However, he does more work when he first lifts a heavier box to chest height.

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instructional diagrams

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questions

any force that is used to move an object does work.

a. true

-->  b. false

work is done when force is applied

a) for a long enough period of time.

b) in the opposite direction that the object moves.

-->  c) in the same direction that the object moves.

d) two of the above

the amount of work done depends on the

a) amount of force applied.

b) distance the object moves.

c) speed with which the object moves.

-->  d) two of the above

you do more work lifting an object if the object is

-->  a) heavier.

b) bigger.

c) harder.

d) warmer.

you do more work playing basketball than you do studying for a test.

-->  a. true

b. false

diagram questions

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