| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.19 |
| Score | 0% | 64% |
A box is resting on a smooth floor. Static friction is present:
when an attempt is made to move the box |
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at all times |
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only if normal force is present |
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if the coefficient of friction is greater than one |
For any given surface, the coefficient of static friction is higher than the coefficient of kinetic friction. More force is required to initally get an object moving than is required to keep it moving. Additionally, static friction only arises in response to an attempt to move an object (overcome the normal force between it and the surface).
The mechanical advantage of a block and tackle is equal to which of the following?
the number of loads |
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the number of connecting ropes |
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the number of input forces |
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the number of pulleys |
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.
| 39 ft⋅lb | |
| 1 ft⋅lb | |
| None of these is correct | |
| 374 ft⋅lb |
What type of load doesn't create specific stress points or vary with time?
non-uniformly distributed load |
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static 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.
Which of the following is not a characteristic of a ceramic?
chemically stable |
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low density |
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high melting point |
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low corrosive action |
Ceramics are mixtures of metallic and nonmetallic elements that withstand exteme thermal, chemical, and pressure environments. They have a high melting point, low corrosive action, and are chemically stable. Examples include rock, sand, clay, glass, brick, and porcelain.