Question

A car is travelling at 20 m/s along a road. A child runs out into the road 50m ahead and the car 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:<br />S=50m<br />u=20m/s<br />v=0m/s (as car stops)<br /><br />v²= u²+2aS<br />0²=20²+2*50*a<br />0=400+100*a<br />a= -400/100<br />a= -4m/s²<br />so,deacceleration is 4m/s².