[CLPhys1 10.P.042.] Worker Pushes Block A worker pushed a 27 kg block 6.2 m along a level floor at constant speed with a force directed 30° below the horizontal.(adsbygoogle = window.adsbygoogle || []).push({});

(a) If the coefficient of kinetic friction is 0.20, what was the work done by the worker's force?

(b) What was the increase in thermal energy of the block-floor system?

This seems like it is supposed to be really easy, but I can't get it.

For (a), I set up a force diagram, and since the block is moving at constant velocity, I knew that F_worker-->block_x = friction, so F_w-->b_x = (mu)_k(m)(g). Since W_worker_x = F_worker-->block_x*(delta x), I just multiplied everything together and then tried to find F_worker-->block by dividing F_worker-->block_x by cos(30). I tried it with cos(60), too, but neither got the right answer.

For part (b), I set W_friction = friction_k * (delta x) * cos(180), but that didn't work either.

I don't know what else to try. I would really appreciate any help anyone can give me!!

Thanks

Beverly

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# Homework Help: Work and Thermal Energy

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