| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.23 |
| Score | 0% | 65% |
Which of the following surfaces would have the highest coefficient of friction?
concrete |
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steel |
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ice |
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marble |
Coefficient of friction (μ) represents how much two materials resist sliding across each other. Smooth surfaces like ice have low coefficients of friction while rough surfaces like concrete have high μ.
Which class of lever offers no mechanical advantage?
third |
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second |
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none of these, all levers offer mechanical advantage |
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first |
A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.
| 8 | |
| 11 | |
| 12 | |
| 16 |
Mechanical advantage is resistance force divided by effort force:
MA = \( \frac{F_r}{F_e} \) = \( \frac{480 lbs.}{60 lbs.} \) = 8
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?
They have done an equal amount of work |
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Sam |
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Lisa |
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Neither have done any work |
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.
Which of these is the formula for kinetic energy?
\(KE = {1 \over 2}mv^2\) |
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\(KE = mgh\) |
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\(KE = {m \over v^2 }\) |
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\(KE = {1 \over 2}mh^2\) |
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.