| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.17 |
| Score | 0% | 63% |
Which of these will have the most impact on the kinetic energy of an object?
its direction |
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its speed |
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its mass |
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its weight |
Kinetic energy is the energy of movement and is a function of the mass of an object and its speed: \(KE = {1 \over 2}mv^2\) where m is mass in kilograms, v is speed in meters per second, and KE is in joules. The most impactful quantity to kinetic energy is velocity as an increase in mass increases KE linearly while an increase in speed increases KE exponentially.
| 6 | |
| 8 | |
| 7.2 | |
| 2 |
The mechanical advantage (MA) of a wedge is its length divided by its thickness:
MA = \( \frac{l}{t} \) = \( \frac{40 in.}{5 in.} \) = 8
Which of the following is not a type of simple machine?
lever |
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screw |
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pulley |
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gear |
The six types of simple machines are the lever, wheel and axle, pulley, inclined plane, wedge, and screw.
A fixed pulley is useful for which of the following?
multiplying the input force |
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changing the direction of the output force |
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multiplying the input distance |
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changing the direction of the input force |
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.
A wedge is most similar to what other type of simple machine?
third-class lever |
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inclined plane |
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second-class lever |
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first-class lever |
The wedge is a moving inclined plane that is used to lift, hold, or break apart an object. A wedge converts force applied to its blunt end into force perpendicular to its inclined surface. In contrast to a stationary plane where force is applied to the object being moved, with a wedge the object is stationary and the force is being applied to the plane. Examples of a wedge include knives and chisels.