| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.01 |
| Score | 0% | 60% |
Sam can do 50 ft. lb. of work in 2 minutes and 5 seconds. What would Sam have to do to increase his power output?
do the work in 3 minutes |
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do 25 ft. lb. of work in 2 minutes 5 seconds |
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do the work in 2 minutes |
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do 100 ft. lb. of work in 4 minutes 12 seconds |
Power is the rate of doing work or \(\frac{W}{t}\). To increase power, increase the work being done in the same amount of time or do the same amount of work in less time.
The work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. This defines which of the following?
mechanical advantage |
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conservation of mechanical energy |
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work-energy theorem |
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Pascal's law |
The work-energy theorem states that the work done by the sum of all forces acting on a particle equals the change in the kinetic energy of the particle. Simply put, work imparts kinetic energy to the matter upon which the work is being done.
According to Boyle's law, for a fixed amount of gas kept at a fixed temperature, which of the following are inversely proportional?
pressure, density |
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density, volume |
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volume, mass |
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pressure, volume |
Boyle's law states that "for a fixed amount of an ideal gas kept at a fixed temperature, pressure and volume are inversely proportional".
Assuming force applied remains constant, which of the following will result in more work being done?
increasing the coefficient of friction |
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moving the object with more speed |
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moving the object farther |
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moving the object with more acceleration |
Work is accomplished when force is applied to an object: W = Fd where F is force in newtons (N) and d is distance in meters (m). Thus, the more force that must be applied to move an object, the more work is done and the farther an object is moved by exerting force, the more work is done.
| 0.67 | |
| 1 | |
| 9.67 | |
| 0.73 |
Because this lever is in equilibrium, we know that the effort force at the blue arrow is equal to the resistance weight of the green box. For a lever that's in equilibrium, one method of calculating mechanical advantage (MA) is to divide the length of the effort arm (Ea) by the length of the resistance arm (Ra):
MA = \( \frac{E_a}{R_a} \) = \( \frac{6 ft.}{9 ft.} \) = 0.67
When a lever is in equilibrium, the torque from the effort and the resistance are equal. The equation for equilibrium is Rada = Rbdb where a and b are the two points at which effort/resistance is being applied to the lever.
In this problem, Ra and Rb are such that the lever is in equilibrium meaning that some multiple of the weight of the green box is being applied at the blue arrow. For a lever, this multiple is a function of the ratio of the distances of the box and the arrow from the fulcrum. That's why, for a lever in equilibrium, only the distances from the fulcrum are necessary to calculate mechanical advantage.
If the lever were not in equilibrium, you would first have to calculate the forces and distances necessary to put it in equilibrium and then divide Ea by Ra to get the mechanical advantage.