Question 7 — Which factors determine the energy - Questions at the end of the chapter - Chapter 7 - Work, Energy, and Simple Machines (Exploration)

Last updated at July 16, 2026 by

Which factors determine the energy required to raise a flag from the ground to the top of a tall flagpole using a pulley? Does raising the flag slowly or quickly change the amount of work done? If the speed at which the flag is raised is doubled, how does the power requirement change? Explain your answers.

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The energy (work) needed depends on the weight of the flag and the height of the pole : W = mgh .

Raising it slowly or quickly does not change the work done (work depends on force and distance, not time).

If the speed is doubled, the time halves, so power P = W t doubles .

What does NOT change
What DOES change
Energy to raise the flag = mgh — it depends only on the mass of the flag and the height of the pole
Power = work ÷ time
Raising it slowly or quickly does not change the work done
Raise it in half the time and you need twice the power
Work is the same either way
So if the speed is doubled , the power requirement is doubled
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