Question

A sled with a mass 47.0 kg is pulled along flat, snow-covered ground. The static friction coefficient is 0.30, and the kinetic 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 at 3.3 m/s2?

Answer 1

(a) The weight of the sled is given by the product of its mass and the acceleration due to gravity:

w = m*g = 47.0 kg * 9.81 m/s^2 = 461.07 N

(b) The force needed to start the sled moving is the maximum force of static friction, which is given by:

f_s = μ_s * w = 0.30 * 461.07 N = 138.32 N

(c) Once the sled is moving at a constant velocity, the force needed to keep it moving is equal to the force of kinetic friction, which is given by:

f_k = μ_k * w = 0.10 * 461.07 N = 46.11 N

(d) The total force needed to accelerate the sled at 3.3 m/s^2 is the sum of the force of kinetic friction and the force required to produce the desired acceleration:

F = f_k + m*a = 46.11 N + 47.0 kg * 3.3 m/s^2 = 200.97 N