| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.29 |
| Score | 0% | 66% |
Two or more pulleys used together are called:
third-class lever |
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wheel and axle |
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gears |
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block and tackle |
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.
Which of the following is the formula for hydraulic pressure?
P = F/A |
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P = FA |
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P = FA2 |
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P = F/A2 |
Hydraulics is the transmission of force through the use of liquids. Liquids are especially suited for transferring force in complex machines because they compress very little and can occupy very small spaces. Hydraulic pressure is calculated by dividing force by the area over which it is applied: P = F/A where F is force in pounds, A is area in square inches, and the resulting pressure is in pounds per square inch (psi).
| 782 lbs. | |
| 783 lbs. | |
| 780 lbs. | |
| 2340 lbs. |
The mechanical advantage (MA) of a block and tackle pulley is equal to the number of times the effort force changes direction. An easy way to count how many times the effort force changes direction is to count the number of ropes that support the resistance which, in this problem, is 4. With a MA of 4, a 195 lbs. effort force could lift 195 lbs. x 4 = 780 lbs. resistance.
What type of load creates different stresses at different locations on a structure?
dynamic load |
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impact load |
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non-uniformly distributed load |
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static uniformly distributed 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.
Which of the following is the formula for gravitational potential energy?
\(PE = { 1 \over 2} mv^2\) |
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\(PE = mgh\) |
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\(PE = { 1 \over 2} mg^2\) |
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\(PE = mg^2h\) |
Gravitational potential energy is energy by virtue of gravity. The higher an object is raised above a surface the greater the distance it must fall to reach that surface and the more velocity it will build as it falls. For gravitational potential energy, PE = mgh where m is mass (kilograms), h is height (meters), and g is acceleration due to gravity which is a constant (9.8 m/s2).