I'm preparing for a grade 11 physics exam but having trouble with a question:
a 19.9kg mass slides in a straight 28.8m line experiencing friction with a coefficient of 0.105, how much thermal energy is produced?
For the force of gravity use $F = m a$ where $a$ is the acceleration of gravity. For the frictional force, multiply this $F$ by the coefficient to get $F_f = \mu F = 0.105 F$. For the thermal energy use $W = F_f\;\; d$, where $W$ is the work and $d$ is the distance.