Question

A car is travelling at 20m/S along a road.A child us out into the road 50m ahead and the car driver steps on the brake pedal.What must be the cars deceleration,if the car is to stop just before it reaches the child.

Answer 1

u=20m/s
v=0m/s
s=50m
${v } ^{2} - u { }^{2} = 2as$
${0}^{2} - ( {20)}^{2} = 2a \times 50$
$- 400 = 100a$
$- 400 \div 100 = a$
$- 4ms { - }^{2} = a$