Question

On a cold day you can warm your hands by rubbing them together. (a) Assume that the coefficient of friction between your hands is 0.5, that the normal force between your hands is 34 N, and that you rub them together at an average speed of 30 cm/s. What is the rate at which heat is generated?

Answer 1

To solve this problem it is necessary to apply the equations related to the Force of Friction and Energy.

By definition the friction force is defined as

$F= \mu * N$

Where,

$\mu =$ Frictional Constant

N = Normal Force -> mg

At the same time we have the definition of the Energy, which can be

E = F*v

Where,

Force

v = Velocity.

Then replacing with our values we have that,

$F = \mu N$

F = 0.5 *34

F = 17

The energy then would be,

E = f v

E = 17 * 0.30 = 5.1 W

Therefore the rate at which heat is generated is 5.1W