A 23.0 kg sled is being pulled across a horizontal surface at a constant velocity. The pulling force has a magnitude of 79.0 N and is directed at an angle of 30.0° above the horizontal. Determine the coefficient of kinetic friction.

Answer 1

YOu have two things here: zero acceleration, and the pulling force upward is helping reduce friction (making normal force less).

vertical component of pulling: 79Sin30, which reduces weight of sled down.

Normal force downward: mg-73sin30
friction force=mu*normal=mu*(mg-73sin30)

horizontal force= 73cos30

netforce=ma
pulling forcehorizontal-frictionforce=0
73cos30-mu(mg-73sin30)=0
solve for mu.