Question

A car is moving in the east direction with the velocity of 30.0 miles/hour. To avoid head on collision the breaks are applied and the car is brought to rest in 10.0s. Calculate the average acceleration of the car?

Answer 1

`-1.3411\ m/s^2`

Explanation:

The acceleration `a` of car moving with initial velocity `u=30\ \text{miles/hr}=13.411\ m/s` brought to rest `v=0` in time `t=10\ sec` is given as follows

`a=\frac{v-u}{t}`

`=\frac{0-13.411}{10}`

`=-1.3411\ m/s^2`

The car is experiences the retardation of `1.3411\ m/s^2`

Answer 2

Car is moving with initial velocity `u=30\ mph`
`=>u=(30xx1760xx3)/3600=44\ ft\ s`
As the car is brought to rest `v=0`
Using the kinematic expression

`v=u+at`,
where `a` is average acceleration
`=>a={v-u}/{t}`

Inserting given values

`a={0-44}/{10}`
`=>a=-4.4\ ft\ s^-2`
It is deceleration.