## College Physics (4th Edition)

The internal energy of the hands has increased by $2.9~J$
We can find the magnitude of the work done by friction: $Work = 8\times F~\mu_k~d$ $Work = 8\times (5.0~N)(0.45)(0.16~m)$ $Work = 2.9~J$ We can assume that the magnitude of the work done by friction is converted into internal energy in the hands. The internal energy of the hands has increased by $2.9~J$