When walking on a flat surface, all the mechanical energy developed to move arms and legs is

eventually dissipated into heat through various friction mechanisms because there is no change in

overall potential energy. However, when we walk uphill, some of the developed mechanical work

gets converted into potential energy of our bodies in Earth's gravity instead of heat. Of course,

walking uphill is harder because we need to supply the additional mechanical power to overcome

gravity.

Measurements show that walking uphill on a $10$ degree slope at $3$ miles per hour approximately

doubles your calories burn rate $($to $460$ food calories per hour$).$ What is the total heat added to the

environment $($in watts$)$ when you are walking horizontally $($without elevation gain$)$ and uphill on a

$10-$degree slope? Again, assume a $140-$lbs human walking at the same $3$ miles per hour both uphill

and on a flat surface. $($Answers: ~~$268W$ and ~~$392W)$