Question

at time 4, what contact forces act on the cart? *
energy transfers and contact forces in the launcher, cart, box, and track system

c) no forces act on the cart
a) force from the launcher
b) air resistance only
d) friction from the track and opposing forces from box

Explanation:

At time 4, the cart is in contact with the track (so there is friction) and the box (so there are opposing forces from the box). The launcher is no longer in contact with the cart (so no force from the launcher). Air resistance is not the only force as there are other contact forces (friction and force from the box).

Answer:

D. Friction from the track and opposing forces from box