Question

If a child ran into the road 65-70 feet ahead of your vehicle, what is the highest speed from which you could stop before hitting him?

Answer 1

the speed of the vehicle should be 57.68 ft/s

Explanation:

Given:

child is running ahead of vehicle by 65-70 ft.

we are given with range of stopping distance

The stopping distance is calculated by

`d =( v^2)/(2\mu g)`

where

μ = 0.8, coefficient of static friction

g = 32ft/s²

now,

`v=√(2\mu g d)\\\\v=√(2*0.8* 32 \ d)\\\\v =7.155√(d)`

at d = 65 ft.

v = 7.155√(65) = 57.68 ft/s

at d = 70 ft.

v = 7.155√(70) = 59.86 ft/s

To be safe, the speed of the vehicle should be 57.68 ft/s