One fateful day, a car with weight \(5000~\mbox{N}\) has malfunctioned on the entry ramp to a highway. It is now sliding down the ramp, angled at \(30^\circ\) with respect to the horizontal. The coefficients (static and kinetic) of friction are \(0.4\). Then, Superman comes and saves the day! However, he just had a fight with the bad guys so he wants to use the least amount of force as possible. First, he uses the minimum amount of force to stop the car. Then, he uses the minimum amount of force to push the car so it starts sliding slightly upward along the ramp. What is the absolute value of the difference between the two forces he uses in Newtons?
Details and assumptions
by
David Mattingly
