Force a man must exert to pull a sled (8334)
A man pulls a sled up a ramp using a rope attached to the front, as illustrated in the figure.

The sled has a mass of 80 kg. The kinetic friction coefficient between the sled and the ramp is (), the angle between the ramp and the horizontal is
, and the angle between the rope and the ramp is
. What force must the man exert to keep the sled moving at a constant speed?