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 35 N, and that you rub them together at an average speed of 35 cm/s. What is the rate at which heat is generated?

(b) Assume further that the mass of each of your hands is approximately 350 g, that the specific heat of your hands is about 4 kJ/kg ∙ K, and that all the heat generated goes into raising the temperature of your hands. How long must you rub your hands together to produce a 5- C^o increase in their temperature?