Conservation of Energy Practice Problems $($In$-$Class, Out$-$of$-$Class but always with Class$)$

$9.$ A $13\mathrm{.}5$ kg sled slides over a $1\mathrm{.}75$ m stretch of horizontal ground where friction is present. Just before it entered this area, its speed was $2\mathrm{.}25\frac{m}{s}.$ Just after leaving it$,$ the sled's speed had been reduced to $1\mathrm{.}20\frac{m}{s}.$ What power was consumed by friction during the sled's slide across the rough surface?

ANS: $-24\mathrm{.}1$ W $($technically negative but usually we just speak of positive power$)$