The minimum distance required to stop a car moving at 35.0 mi/h is 40.0 ft. What is
the minimum stopping distance for the same car moving at 70.0 mi/h, assuming the
same rate of acceleration?

Question

The minimum distance required to stop a car moving at 35.0 mi/h is 40.0 ft. What is 
the minimum stopping distance for the same car moving at 70.0 mi/h, assuming the 
same rate of acceleration?

mrnood · Answer

v^2= u^2 +2as

in the initial state you have s, v and u   (v=0 as the car has stopped)
You need to convert the units mph to ft/s

then use the same equation for the second part - you have v,u and a so calculate s