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

Answer:

the speed of the vehicle should be 57.68 ft/s

Step-by-step 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

$d =\dfrac{ v^2}{2\mu g}$

where

μ = 0.8, coefficient of static friction

g =  32ft/s²

now,

$v=\sqrt{2\mu g d}\\\\v=\sqrt{2\times0.8\times 32 \ d}\\\\v =7.155\sqrt{d}$

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