| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 2.87 |
| Score | 0% | 57% |
Depending on where you apply effort and resistance, the wheel and axle can multiply:
force or speed |
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speed or power |
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force or distance |
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power or distance |
If you apply the resistance to the axle and the effort to the wheel, the wheel and axle will multiply force and if you apply the resistance to the wheel and the effort to the axle, it will multiply speed.
A box is resting on a smooth floor. Static friction is present:
when an attempt is made to move the box |
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if the coefficient of friction is greater than one |
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only if normal force is present |
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at all times |
For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).
| 450 lbs. | |
| 153 lbs. | |
| 150 lbs. | |
| 152 lbs. |
The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 6. With a MA of 6, a 25 lbs. effort force could lift 25 lbs. x 6 = 150 lbs. resistance.
Which of the following represents the force a surface exerts when an object presses against it?
normal force |
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counter force |
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friction |
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mass |
Normal force (FN) represents the force a surface exerts when an object presses against it.
Concurrent forces:
act in a common plane |
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act along the same line of action |
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pass through a common point |
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act in a common dimension |
Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.