WORK. A 2 kg mass is spun on a string in a horizontal circular path at a constant speed.

a. Draw the free-body diagram for the mass.

b. If the radius of the path is 0.5 m and the period of revolution is 0.25 s, what is the speed of the mass

c. What force is keeping the mass in a circular path?

d. What is the net force acting on the mass in the horizontal direction?

A47.2 g block of copper whose temperature is 480 k is placed in an insulating box with a 91.8 g block of lead whose temperature is 200 k. (a) what is the equilibrium temperature of the two-block system? (b) what is the change in the internal energy of the two-block system between the initial state and the equilibrium state? (c) what is the change in the entropy of the two-block system? the heat capacities of copper and lead are 386 j/kg·k and 128 j/kg·k, respectively.