A sled of mass 51 kg is pulled along snow-covered, flat ground. The static friction coefficient is 0.30, and the sliding friction coefficient is 0.10.

(a) What does the sled weigh?

(b) What force will be needed to start the sled moving?

(c) What force is needed to keep the sled moving at a constant velocity?

(d) Once moving, what total force must be applied to the sled to accelerate it 4.4 m/s2?