Question

The driver of an automobile moving with a speed of 36kmph sees a child standing in the middle of a

road and brings his vehicle to rest in 4s just in time to save the child. What is the average retarding force

on vehicle? The mass of the automobile is 1200kg and the mass of the driver is 50 kg.​

Answer 1

Answer:

$v = u + at \\ 0 = 20 +( - a)4 \\ 4a = 20 \\ a = 5ms^{ - 2}$

36 kmph equals to 20mps

$f = ma \\ = (1200 + 50) \times 5 \\ = 7250n$