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amm1812
3 years ago
7

A motor is used to lift a 10 kg mass 2 m above the ground in 4 s. If the power input to the motor is 100 W. what is the efficien

cy of the motor?
(Show Work)
Physics
1 answer:
Bad White [126]3 years ago
7 0

Answer:

98%

Explanation:

Given parameters

Mass of motor = 10kg

Height = 2m

Time = 2s

Power input = 100w

Unknown

Efficiency = ?

Solution

Efficiency is the percentage of the power output to the power input.

Power is the rate at which work is done.

Power output = mass x g x height / time

g is the acceleration due to gravity

Power output = 10x 2 x 9.8 / 2 = 98W

Efficiency = power output/ power input x 100

Efficiency = 98/100 x 100 = 98%

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Answer:

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Explanation:

We could use the following suvat equation:

s=vt-\frac{1}{2}gt^2

where

s is the vertical displacement of the coin

v is its final velocity, when it hits the water

t is the time

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Taking upward as positive direction, in this problem we have:

s = -1.2 m

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And the coin reaches the water when

t = 1.3 s

Substituting these data, we can find v:

v=\frac{s}{t}+\frac{1}{2}gt=-\frac{1.2}{1.3}+\frac{1}{2}(-9.8)(1.3)=-7.3 m/s

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3 years ago
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Answer:

Option (d) is correct.

Explanation:

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Unit of work is Joule (J) and that of time is second (s). It means that the unit of power is Watt and it is equal to Joule/second

Hence, the correct option is (d) "The unit for work is a joule. The unit for power is a watt, which is a joule per second".

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