Question

A car is travelling at 20m per second along a road. A child runs out into the road 50 m ahead and the car Driver steps on the brake pedal. What must the cars retardation be if the car is to stop just before it reaches the child

Answer 1

GIVEN ;-

⇒ Speed of the car = 20 m / s

⇒ Distance of the child from the car when it goes into the road = 50m

TO FIND ;-

⇒  What must the car’s deceleration be if the car is to stop just before it reaches the child?

SOL ;-

⇒ Distance of the child from the car in the road ( S ) = 50 m

⇒ Initial velocity of the car ( u ) = 20 m / s

⇒Final velocity of the car ( v )   = 0 m / s

Now let us find the acceleration using the formula -

                           2 a s = v² - u ²

Here we need to find the acceleration so let us rearrange the formula ,

we get as -                            a = u² - v² / 2 as

                               ⇒  a = v² - u² / 2 s

                               ⇒  a = 0 - 20² / 2 × 50

                               ⇒  a = -  400 / 100 

                               ⇒ a =    -  4 m /s

                           So acceleration is - 4 m /s