Am I overthinking this physics question?

[Novis619]

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From TBR: Imgur

I know that PE=mgh and 98 = (1)(9.8)(h) ---> h = 9.8 or 10m. But because this method is only 10% efficient, shouldn't we multiply the height by 10 to get 100m? The answer in the back stops at 10m (which is the correct answer) and doesn't even mention efficiency in the explanation.

Thanks in advance.

 

[milski]

What is given in the table is the total energy of the source, that would be the energy put in, not what you are able to extract. The 10% will be applied on this amount to determine the final energy delivered.

 

[Novis619]

That makes sense, thanks.