Physics help, please explain why so i can learn it?

Question

1. A driver begins to brake when her car is traveling at 14.0 m/s, and the car comes to a stop 3.5 s later. How much further does the car go after she begins to brake, assuming the acceleration is constant?
and
2. A penny dropped from the top of a tower would hit the pavement below in 5.3 s. How tall is the tower?

if oy know only one, please help me with it, i will be very gratefull

Answer 1

OK
1. The velocity is 14 M/s and acceleration is
constant so if the stop takes 3.5 sec. then the average velocity is 14 m/s divided by 2 and the distance is
the average x 3.5 sec. (or 7m/s x 3.5s), or 24.5m.

2. Again the acceleration is constant.
'G`. (Find it in your book.)
If you multiply G by 5.3 sec.s, you have the
end velocity. If you halve this number, you
have the average velocity.
This average x the time, (5.3 sec.) will give you
the distance .