| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 2.72 |
| Score | 0% | 54% |
Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?
do the work in 2 minutes |
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do the work in 3 minutes |
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do 100 ft. lb. of work in 4 minutes 12 seconds |
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do 25 ft. lb. of work in 2 minutes 5 seconds |
Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.
The mechanical advantage of connected gears is proportional to which characteristic of the gears?
speed |
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number of teeth |
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diameter |
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circumference |
The mechanical advantage (amount of change in speed or torque) of connected gears is proportional to the number of teeth each gear has. Called gear ratio, it's the ratio of the number of teeth on the larger gear to the number of teeth on the smaller gear. For example, a gear with 12 teeth connected to a gear with 9 teeth would have a gear ratio of 4:3.
What's the last gear in a gear train called?
driven gear |
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idler gear |
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output gear |
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driver gear |
A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.
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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changing the direction of the input force |
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multiplying the input distance |
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 principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?
kinetic energy |
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potential energy |
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total mechanical energy |
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acceleration |
As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.