Physics still don't get it
posted by Anonymous .
Given: g=9.81 m/s square.
The parachute on a race car that weighs 8042 N opens at the end of a quartermile run when the car is traveling 35 m/s. What net retarding force must be supplied by the parachute to stop the car in a distance of 1020 m? Answer in units of N.

m = weight in Newtons/ 9.81
Change in kinetic energy = average force * distance.
The change in KE is all the KE, since it stopped.
(1/2) m v^2 at the start = F * 1020
So F = (1/2) m v^2 / 1020