A distance of d is covered with 53 mile/hr initially.
Time taken to cover this distance t1 = d/53 hour
Next distance of d is covered with x mile hours.
Time taken to cover this distance t2 = d/x hours.
We have average speed = 26.5 mile / hour
= Total distance traveled/ total time taken
= 

The sentence can be completed as follows:
"Electricity is the movement of charges from one atom to another along a conductor."
The movement of the the charges is due to the presence of a potential difference across the conductor, which pushes the charges. More specifically, in normal conductors, the carriers of electricity are the electrons. Therefore we can rewrite the sentence as
"Electricity is the movement of electrons from one atom to another along a conductor."
Quantum theory is the theoretical basis of modern physics that explains the nature and behavior of matter and energy on the atomic and subatomic level. The nature and behavior of matter and energy at that level is sometimes referred to as quantum physics and quantum mechanics.
The car bounces off and moves in the opposite direction