physics question

Question

A driver brings a car to a full stop in 2.0 s. 

1. If the car was initially traveling at 22 m/s, what was the acceleration?
2. How far did the car travel during braking?

Answer 1

Hi Gin,

Here is how I would do this question.

For Part 1:

We know the following information from the problem:

Vf = 0

Vo = 22m/s

a = ?

d = ? (Part 2)

t = 2.0s

Using the above information, I can easily use the following equation:

Vf = Vo + at

a = (Vf - Vo) /t = (0 - 22)/2 = -11m/s^2

Therefore the acceleration of the vehicle is - 11m/s^2.

For Part 2:

We know the following information:

Vf=0

Vo=22

a=-11 (Found in Part 1)

d=?

t=2

Given the above, I can easily use the following equation: Vf^2 = Vo^2 +2ad

Vf^2 = Vo^2 + 2ad

d = (Vf^2 - Vo^2)/2a = (0^2 - 22^2)/(2(-11)) = -484/-22 = 22 m

The distance traveled by the vehicle as it is coming to rest in 2.0s is 22m.