Tag: work and power

Questions Related to work and power

If the heart pushes 1 cc of blood in one second under pressure of 20000$Nm^{-2}$, the power of heart is

power work and power energy and its forms work, energy and power physics

  1. 0.02 W

  2. 400 W

  3. $5\times 10^{-10}W$

  4. 0.2 W

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Correct Option: A
Explanation:

Given,

$P=20000Nm^{-2}$
$\dfrac{dV}{dt}=1cc/s$
Power, $P=\dfrac{W}{t}=F.v=PA\dfrac{dx}{dt}$   (as, $F=PA$)
$P=P.\dfrac{dV}{dt}$
$P=20\times 10^3\times \dfrac{1}{(10^2)^3}$
$P=\dfrac{2}{100}=0.02W$
The correct option is A.

A pump can hoist 9000 kg of coal per hour from a mine of 120 m deep. calculate the power of the pump, in watts, assuming its efficiency is 75%, g=9.8 $m/s^{2}$

power work and power energy and its forms work, energy and power physics

  1. 3.92 watts

  2. 39.2 watts

  3. 392 watts

  4. 3920 watts

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Correct Option: D

A man starts walking from a point on the surface of earth (assumed smooth) and reaches diagonally opposite point. What is the work done by him? 

power work and power energy and its forms work, energy and power physics

  1. Zero

  2. Positive

  3. Negative

  4. Nothing can be said

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Correct Option: A

The power of water pump is 4 kW. If g = 10 $ms^{-2}$, the amount of water it can raise in 1 minute to a height of 20 m is 

power work and power energy and its forms work, energy and power physics

  1. 100 litre

  2. 1000 litre

  3. 1200 litre

  4. 2000 litre

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Correct Option: C