A cart slides down a frictionless inclined track to a circular loop of radius R = 13 m. In order for the cart to negotiate the loop safely, the normal force acting on the cart at the top of the loop, due to the track, must be at least equal to the cart's weight. (Note: This is different from the conditions needed to just negotiate the loop.) a) What must be the minimum speed |vmin| of the cart at the top of the loop? For this question, I did sq rt. (13 x 9.81) and got 11.293, but thats not the right answer. b) How high h above the top of the loop must the cart be released? c) When the car is descending vertically in the loop (point (c) in the picture), what is its speed |v|? d) At the bottom of the loop, on the flat part of the track, the cart must be stopped in a distance of d = 10 m. What returning acceleration |a| is required? I dont think I can do the rest without knowing a first.