The south poles of two bar magnet are 10 cm from each other. The poles are brought to 5 cm apart and then moved back to their original positions. How does the energy of the system change?

The potential energy of the system first decreases and then increases.

The total change in the energy of the system is zero.

Both the potential and kinetic energy of the system decrease.

The kinetic energy of the system decreases because some of it is transferred to thermal energy,
d

Balloon a has charge q, and identical mass balloon b has charge 10q. you hang them from threads near each other. choose all of the statements with which you agree. check all that apply. a. a and b exert the same magnitude forces on each other. b. the force that a exerts on b is 10 times the force that b exerts on a. c. the angle between the thread supporting a and the vertical is < the angle between the thread supporting b and the vertical. d. the force that a exerts on b is 1/10 the force that b exerts on a.