| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.44 |
| Score | 0% | 69% |
The standard unit of energy is the:
Volt |
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Horsepower |
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Watt |
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Joule |
The Joule (J) is the standard unit of energy and has the unit \({kg \times m^2} \over s^2\).
Lisa lifts a 25 pound box from the floor onto a loading dock 4 ft. off the ground. Sam slides the same box along a ramp to move it up another 4 ft. onto a flatbed truck. Who has done more work?
Lisa |
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Neither have done any work |
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They have done an equal amount of work |
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Sam |
Work is force multiplied by distance. Because both Connie and Sam moved the same weight the same distance they have done an equal amount of work. Sam employed the mechnacial advantage of an inclined plane so he exerted less effort to do the work but the amount of work done was still the same.
| 800 ft⋅lb | |
| 8 ft⋅lb | |
| 200 ft⋅lb | |
| 66 ft⋅lb |
Friction resists movement in a direction __________ to the movement.
opposite |
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perpendicular |
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parallel |
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normal |
Friction resists movement. Kinetic (also called sliding or dynamic) friction resists movement in a direction opposite to the movement. Because it opposes movement, kinetic friction will eventually bring an object to a stop. An example is a rock that's sliding across ice.
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 25 ft. lb. of work in 2 minutes 5 seconds |
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do the work in 2 minutes |
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do 100 ft. lb. of work in 4 minutes 12 seconds |
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do the work in 3 minutes |
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.