| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.25 |
| Score | 0% | 65% |
Two or more pulleys used together are called:
gears |
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third-class lever |
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block and tackle |
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wheel and axle |
Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.
| 0.08 ft. | |
| 0.15 ft. | |
| 0.04 ft. | |
| 0.05 ft. |
To balance this lever the torques at the green box and the blue arrow must be equal. Torque is weight x distance from the fulcrum so the equation for equilibrium is:
Rada = Rbdb
where a represents the green box and b the blue arrow, R is resistance (weight/force) and d is the distance from the fulcrum.Solving for db, our missing value, and plugging in our variables yields:
db = \( \frac{R_ad_a}{R_b} \) = \( \frac{10 lbs. \times 1 ft.}{65 lbs.} \) = \( \frac{10 ft⋅lb}{65 lbs.} \) = 0.15 ft.
What type of load creates different stresses at different locations on a structure?
impact load |
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non-uniformly distributed load |
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static uniformly distributed load |
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dynamic 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.
What type of load acts on a relatively small area of a structure?
dynamic load |
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non-uniformly distributed load |
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concentrated load |
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impact 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 a wheel and axle is equal to the:
ratio of the diameters of the wheels |
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difference in the diameters of the wheels |
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difference in the lengths of the axles |
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length of the axle |
A wheel and axle uses two different diameter wheels mounted to a connecting axle. Force is applied to the larger wheel and large movements of this wheel result in small movements in the smaller wheel. Because a larger movement distance is being translated to a smaller distance, force is increased with a mechanical advantage equal to the ratio of the diameters of the wheels. An example of a wheel and axle is the steering wheel of a car.