Question

A dog (mass 12.3 kg) sits on a sled (mass 5.1 kg) that is being pushed with a force of 33 N on a flat snowy surface. If the acceleration of both is 1.5 m/s2, what is the coefficient of kinetic friction for the sled sliding on the snow?

Answer 1

First, you need to calculate the resultant force:
R = m · a
   = (12.3 + 5.1) · 1.5
   = 26.1 N

Then, you can calculate the force of friction:
R = F - Fₐ
Fₐ = F - R
    = 33 - 26.1
    = 6.9 N

Now, we know that:
Fₐ = μ·m·g
Therefore we can solve for μ:

μ = Fₐ/mg
   = 6.9 / (17.4 · 9.8)
   = 0.40 

The coefficient of dynamic friction is μ = 0.40