Recently a light powered by gravity has been gaining attention as an option for off-grid lighting. A falling weight pulls a cable to drive a generator, producing power for a LED light. (When the weight gets to the bottom, it must be lifted to begin the power generation again. In this sense it is a human powered light.

Question: What is the maximum average power (in watts) that can be generated by letting the 5 kg weight fall the 1.5 meters back to the floor in 15 minutes?

I'd appreciate any ideas. Thanks! :)

Question

Recently a light powered by gravity has been gaining attention as an option for off-grid lighting.  A falling weight pulls a cable to drive a generator, producing power for a LED light. (When the weight gets to the bottom, it must be lifted to begin the power generation again.  In this sense it is a human powered light.

Question: What is the maximum average power (in watts) that can be generated by letting the 5 kg weight fall the 1.5 meters back to the floor in 15 minutes?

I'd appreciate any ideas. Thanks! :)

anonymous · Answer

the average power would be the total work done by the object divided by the time taken by it so

$$power=\frac{ work}{ time }  $$   
and work will be equal to the weight (gravitational force exerted on the object) multiplied with the distance covered by the object so 

$$work=weigh * distance= mgh$$

where 'm' is the mass of object , 'g' is gravitational acceleration and 'h' is the distance traveled by the object therefore

$$power=\frac{ mgh }{ t }=\frac{ 5*9.8*1.5 }{ 15*60}=81.7mW$$

time is taken in seconds and mW is miliwatts

anonymous · Answer

Perfect explanation and answer, Thanks!

anonymous · Answer

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