| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 2.46 |
| Score | 0% | 49% |
Which of the following represents the force a surface exerts when an object presses against it?
normal force |
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friction |
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mass |
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counter force |
Normal force (FN) represents the force a surface exerts when an object presses against it.
Which of the following is the formula for gravitational potential energy?
\(PE = { 1 \over 2} mg^2\) |
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\(PE = { 1 \over 2} mv^2\) |
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\(PE = mg^2h\) |
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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).
Torque involves a perpendicular force applied to a lever arm that moves around a center of rotation. Increasing the length of the lever arm will do which of the following?
decrease torque |
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decrease applied force |
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increase applied force |
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increase torque |
Torque measures force applied during rotation: τ = rF. Torque (τ, the Greek letter tau) = the radius of the lever arm (r) multiplied by the force (F) applied. Radius is measured from the center of rotation or fulcrum to the point at which the perpendicular force is being applied. The resulting unit for torque is newton-meter (N-m) or foot-pound (ft-lb).
Which class of lever offers no mechanical advantage?
first |
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none of these, all levers offer mechanical advantage |
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third |
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second |
A third-class lever is used to increase distance traveled by an object in the same direction as the force applied. The fulcrum is at one end of the lever, the object at the other, and the force is applied between them. This lever does not impart a mechanical advantage as the effort force must be greater than the load but does impart extra speed to the load. Examples of third-class levers are shovels and tweezers.
What's the last gear in a gear train called?
driver gear |
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output gear |
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idler gear |
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driven gear |
A gear train is two or more gears linked together. Gear trains are designed to increase or reduce the speed or torque outpout of a rotating system or change the direction of its output. The first gear in the chain is called the driver and the last gear in the chain the driven gear with the gears between them called idler gears.