A bobsledder pushes her sled across horizontal snow to get it going, then jumps in. After she jumps in, the sled gradually slows to a halt. What forces act on the sled just after she's jumped in?

a) Gravity and kinetic friction

b) Gravity and normal force

c) Gravity and the force of the push

d) Gravity, a normal force, and kinetic friction

e) Gravity, a normal force, kinetic friction, and the force of the push

d) Gravity, a normal force, and kinetic friction

Explanation:

When the bobsledder pushes her sled across horizontal snow to get it going, after she jumps into the sled there acts a force of gravity on the total mass of the sled including the bobsledder. The sled moves horizontally and not vertically this means that there is a normal force acting in the vertically upward direction opposite to the gravity. While the sled moves on the horizontal surface and comes to the rest there acts a kinetic frictional force on the body in the direction opposite to the direction of motion.