Question

if a car traveling at 31.5 m/s is brought to a full stop in 4.00 s after the brakes are applied, find the average acceleration during braking. if the acceleration is in the direction of the car's velocity, enter a positive value. if the acceleration is in the direction opposite to the car's velocity, enter a negative value.

Answer 1

The car's average acceleration during braking was -7.875
`m/s^2`

Step-by-step explanation:

We can use this kinematics equation to evaluate the acceleration of the car

`a=(v_f-v_o)/(t)`

`a` is the acceleration

`v_f` is the final velocity

`v_o` is the initial velocity

`t` is the time

Since it says "brought to a full stop" we can say the final velocity is 0 m/s.

Numerical Evaluation

In this example we are given

`v_o=31.5\\v_f=0\\t=4`

Substituting our given values into the equation yields

`a=(0-31.5)/(4)`

Lets solve for
`a`.

Subtract
`31.5` from
`0`.

`a=(-31.5)/(4)`

Divide
`-31.5` by
`4`.

`a=-7.875`