| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 2.99 |
| Score | 0% | 60% |
What type of load doesn't create specific stress points or vary with time?
impact load |
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concentrated 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.
| 803 lbs. | |
| 793 lbs. | |
| 2400 lbs. | |
| 800 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 200 lbs. effort force could lift 200 lbs. x 4 = 800 lbs. resistance.
Which of the following is the formula for gravitational potential energy?
\(PE = { 1 \over 2} mv^2\) |
|
\(PE = mg^2h\) |
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\(PE = { 1 \over 2} mg^2\) |
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\(PE = mgh\) |
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).
The principle of conservation of mechanical energy states that, as long as no other forces are applied, what will remain constant as an object falls?
potential energy |
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kinetic energy |
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acceleration |
|
total mechanical energy |
As an object falls, its potential energy is converted into kinetic energy. The principle of conservation of mechanical energy states that, as long as no other forces are applied, total mechanical energy (PE + KE) of the object will remain constant at all points in its descent.
| 0 ft⋅lb | |
| 1 ft⋅lb | |
| 23100 ft⋅lb | |
| 24 ft⋅lb |