| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.61 |
| Score | 0% | 72% |
The force required to initally get an object moving is __________ the force required to keep it moving.
lower than |
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higher than |
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opposite |
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the same as |
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).
Friction between two or more solid objects that are not moving relative to each other is called:
gravitational friction |
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static friction |
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kinetic friction |
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dynamic friction |
Static friction is friction between two or more solid objects that are not moving relative to each other. An example is the friction that prevents a box on a sloped surface from sliding farther down the surface.
Which of the following will increase the mechanical advantage of a second-class lever?
move the fulcrum between the force and the object being lifted |
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move the object being lifted farther away from the fulcrum |
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move the object being lifted closer to the fulcrum |
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decrease the length of the lever |
A second-class lever is used to increase force on an object in the same direction as the force is applied. This lever requires a smaller force to lift a larger load but the force must be applied over a greater distance. The fulcrum is placed at one end of the lever and mechanical advantage increases as the object being lifted is moved closer to the fulcrum or the length of the lever is increased. An example of a second-class lever is a wheelbarrow.
A fixed pulley has a mechanical advantage of:
1 |
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0 |
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-1 |
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2 |
A fixed pulley is used to change the direction of a force and does not multiply the force applied. As such, it has a mechanical advantage of one. The benefit of a fixed pulley is that it can allow the force to be applied at a more convenient angle, for example, pulling downward or horizontally to lift an object instead of upward.
The steering wheel of a car is an example of which type of simple machine?
fixed pulley |
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block and tackle |
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first-class lever |
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wheel and axle |
A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.