Pilar rubs two balloon against her hair. Each balloon becomes negatively charged with equation. She holds the balloons 0.7 m apart.

a) What is the force between the two balloons?

b) Is this force attractive or repulsive?

Question 21 options:

1)

0.73 N, repulsive

2)

0.73 N, attractive

3)

0.018. repulsive

4)

0.018, attractive

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.