An apple fell 4 m from the top of the tree to the ground in 0.9 s. what was its average speed?
a. 3.6 m/s
b. 4.0 m/s
c. 4.4 m/s
d. 4.5 m/s down

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.