Answer:
C. molecules speed up as more thermal energy is added
Explanation:
The molecules will simply speed up as more thermal energy is added to the solid.
Thermal energy is a form of kinetic energy which is set in motion.
- Heat causes kinetic energy build up in a body.
- As the molecules of the solid gains heat, they will continue to increase in thermal energy.
- They are forced to start vibrating about their fixed point.
- Thereafter, when they have enough energy, they break free from the forces holding them.
- Therefore, they move from a state of rest to one with a very high kinetic energy where the molecules moves rapidly.
- This is why a solid will change to liquid and sometimes eventually gas
Answer:
c) The distance between the balls increases.
Explanation:
If you drop the balls at the same time, regardless of their masses they accelerate equally, since they will be in free fall.
However, if you drop one of the balls earlier, then that ball will gain velocity, whereas the second ball has zero initial velocity. At the time the second ball is dropped, both balls have the same acceleration but different initial velocities.
According to the below kinematics equation:

The initial velocity of the first ball will make the difference, and the first ball will travel a greater distance than the second ball. Hence, their distance increases.