| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.15 |
| Score | 0% | 63% |
| 52.4 lbs. | |
| 65.4 lbs. | |
| 55.3 lbs. | |
| 61.4 lbs. |
This problem describes an inclined plane and, for an inclined plane, the effort force multiplied by the effort distance equals the resistance force multipied by the resistance distance:
Fede = Frdr
Plugging in the variables from this problem yields:
Fe x 7 ft. = 430 lbs. x 1 ft.
Fe = \( \frac{430 ft⋅lb}{7 ft.} \) = 61.4 lbs.
Which of the following represents how much two materials resist sliding across each other?
normal friction |
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kinetic friction |
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coefficient of friction |
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static friction |
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.
The mass of an object correlates to the size of the object but ultimately depends on:
the object's density |
|
the object's potential energy |
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the object's weight |
|
gravity |
Mass is a measure of the amount of matter in an object. In general, larger objects have larger mass than smaller objects but mass ultimately depends on how compact (dense) a substance is.
What type of load varies with time or affects a structure that experiences a high degree of movement?
dynamic load |
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static load |
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impact load |
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concentrated load |
A concentrated load acts on a relatively small area of a structure, a static uniformly distributed load doesn't create specific stress points or vary with time, a dynamic load varies with time or affects a structure that experiences a high degree of movement, an impact load is sudden and for a relatively short duration and a non-uniformly distributed load creates different stresses at different locations on a structure.
The mechanical advantage of connected gears is proportional to which characteristic of the gears?
speed |
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diameter |
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circumference |
|
number of teeth |
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.