Question

What was the initial speed of a car if its speed is 40 m/s after 5 seconds of accelerating at -4 m/s2?

Answer 1

60m/s

Step-by-step explanation:

We are given that

Speed of car after 5 sec, v=40m/s

Acceleration ,a=
`-4m/s^2`

We have to find the initial speed of car.

We know that

Acceleration, a=
`(v-u)/(t)`

Where v=Final speed

u=Initial speed

Using the formula

`-4=(40-u)/(5)`

`-4* 5=40-u`

`-20=40-u`

`u=40+20`

`u=60`

Hence, initial speed of car=60m/s