Question

By how much does the entropy of the universe increase when you drop your pencil off your desk?

Answer 1

Assume that

mass of the pencil, m = 50 g = 0.05 kg

height of the desk, h = 1 m

Temperature of the room, T = 300 K

Now,

After the pencil drops on the floor and system reaches equilibrium, potential energy of the pencil converts into the heat at the room temperature since the system is very large i.e universe

Now,

Change in entropy, S = potential energy of the pencil / Temperature

                                     = m*g*h / T = (0.05*9.8*1) / 300

                                     = 0.49 / 300 = 1.63 * 10^-3 J/K