Question

A car is travelling at 20 m / s 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 car's declaration be if the car is to stop just before it reaches the child. ?

Answer 1

Answer:

4 m/s^2

Explanation:

According to the given question,

v = final velocity = 0 m/s

u = initial velocity = 20 m/s

s = displacement = 50 m

a = acceleration/deceleration =?

And we are asked to find the deceleration of the car such that it wont hit the child.

We know,

• v^2 = u^2 +2as

(Putting the values)

• 0 = 400 + 2×a×50

• a = -(400/100)

• a = -4 m/s^2 ans.

(The negative sign shows that its decelerating whereas the 4 m/s^2 is its magnitude)

So the car needs the deceleration of 4 m/s^2 such that it wont hit the child.