A classical mechanics problem by akwesi barnes

To determine whether the car has hit any person , we need to find the distance it travels after applying the brakes.

From the problem , we know that

$u=20m/s$

$v=0m/s$

$a=-2m/s^2$

From third equation of motion ,

$v^2-u^2=2as$

Plugging in the values , we get $s=100m,$ indicating that the car did not hit any person.

Therefore our required answer is the distance from the crowd the car stops. Answer = $120-100m = 20m.$

Therefore the answer is $20m.$

To know whether there was anyone knocked down by the car, there is the need to find the distance for the car travelled after the brake was applied before it finally came to stop.initial velocity, u=20m/s;final velocity, v=0m/s;retardation, a=-2m/s. using the 3rd equation,v^2=u^2+2as. s=(v^2-u^2)divided by2a. s=100m.therefore if the distance was 120m then the car stopped 20m away from the demonstrators