Ahmed saw all of these things as he walked to school this morning. Which one is an example of a force pushing downward toward the ground?

A. A bird sat on a telephone wire.
B. A woman moved her child from one place to another in a wagon.
C. A man pulled weeds in his garden.
D. A dog tugged on a rope a child held.

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.