| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.18 |
| Score | 0% | 64% |
Normal force is generally equal to the __________ of an object.
mass |
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weight |
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density |
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coefficient of friction |
Normal force arises on a flat horizontal surface in response to an object's weight pressing it down. Consequently, normal force is generally equal to the object's weight.
Hydraulics is the transmission of force through the use of which of the following?
torque |
|
air pressure |
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liquids |
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gear systems |
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).
| 20 ft. | |
| 0 ft. | |
| 5 ft. | |
| 42 ft. |
Win = Wout
Feffort x deffort = Fresistance x dresistance
In this problem, the effort work is 850 ft⋅lb and the resistance force is 170 lbs. and we need to calculate the resistance distance:
Win = Fresistance x dresistance
850 ft⋅lb = 170 lbs. x dresistance
dresistance = \( \frac{850ft⋅lb}{170 lbs.} \) = 5 ft.
| 8.7 | |
| 4.3 | |
| 4.8 | |
| 2.2 |
The mechanical advantage of a gear train is its gear ratio. The gear ratio (Vr) is the product of the gear ratios between the pairs of meshed gears. Let N represent the number of teeth for each gear:
Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) \( \frac{N_3}{N_4} \) ... \( \frac{N_n}{N_{n+1}} \)
In this problem, we have three gears so the equation becomes:
Vr = \( \frac{N_1}{N_2} \) \( \frac{N_2}{N_3} \) = \( \frac{26}{20} \) \( \frac{20}{6} \) = \( \frac{26}{6} \) = 4.3
Two gears are connected and the larger gear drives the smaller gear. The speed of rotation will __________ and the torque will __________.
decrease, increase |
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decrease, decrease |
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increase, increase |
|
increase, decrease |
Connected gears of different numbers of teeth are used together to change the rotational speed and torque of the input force. If the smaller gear drives the larger gear, the speed of rotation will be reduced and the torque will increase. If the larger gear drives the smaller gear, the speed of rotation will increase and the torque will be reduced.