How much work is done in an hour?

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SUMMARY

The discussion centers on calculating the work done by a man pumping water at a rate of 20 liters per minute to a height of 10 meters. The correct power output is determined using the formula P = ΔE/ΔT, where ΔE is the energy change due to lifting the water. The initial calculation mistakenly used minutes instead of seconds, leading to an incorrect unit of measurement. The accurate power output is 32.67 J/s, which translates to Watts, and to find the total work done in an hour, this value must be multiplied by the total seconds in an hour.

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  • Understanding of basic physics concepts, specifically work and energy.
  • Familiarity with the formula for power (P = ΔE/ΔT).
  • Knowledge of unit conversions, particularly between minutes and seconds.
  • Basic understanding of gravitational force (9.8 m/s²).
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  • Calculate total work done using the formula W = P × t, where t is the total time in seconds.
  • Explore the implications of neglecting friction in work calculations.
  • Learn about energy conversion in mechanical systems.
  • Study the relationship between power, work, and time in physics.
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Homework Statement


A man pumps water at a rate of 20 liters per minute to a height of 10 meters. How much work does he do in an hour? Friction is to be neglected. A liter of water is taken to weigh 1 kilogram.



Homework Equations





The Attempt at a Solution


If 1 liter=1 Kilogram then 20 liters = 20 kg
Work is a kind of energy conversion. The work done per unit of time is
P= ΔE/ ΔT = (20)(9.8)(10)/(60minutes) = 32.67J/minute

Is this correct? I'm unsure about the conversions?
 
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Your answer for the power is correct, but you should divide by 60 seconds, not 60 minutes, and the answer would then be in J/s, or W You need to multiply that with the number of seconds in an hour to get the answer to the question.
 
So the correct answer would be:
P = ΔE/ ΔT = (20)(9.8)(10)/(60seconds) = 32.67J/seconds
 

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