Question

a car is traveling at 20 m/ s along a road .a child must out onto the road 50 m ahead and the driver steps on the brake pedal. what must the car's deceleration 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 .