A person pulls her 70 N bag 200 meters at a constant speed.(adsbygoogle = window.adsbygoogle || []).push({});

The force exerted is 40 N at 50 degrees.

I can figure out the work the person does (5142 J).

But I'm having trouble figuring out the 'work done by the force of friction'

I know that Wfriction = delta KE + delta PE

...Since the speed is constant KE should be 0, but I'm not sure what to do about PE.. I know PE = mgy and delta PE = PEfinal - PEinitial but since it's a horizontal surface wouldn't that be 0? I must be doing something wrong because it can't be 0..

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# Homework Help: Friction and work

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