Question

A motorist moving at 44m/s finds a child on the road 100m away. He aplies brakes so as to stop the vehicle within 1 m of the child. Calculate the time required

Answer 1

now u = 44 m per second
v = 0
s = 100 - 1 = 99 m ( just 1 m before child)
let time required to be "t"
so a = v - 44 divided by t
a = -44 / t
we know the equation
s = ut + half at^2
99 = 44t + (-22t)
99 = 22t
4.5 seconds = time required