Question

A piano has a mass of 185 kg, and the coefficient of friction between it and the floor is 0.39. What is the maximum force of friction between the piano and the floor?
707 N
523 N
1813 N
1208 N

Answer 1

The mass of the piano is 185 kg, therefore its weight is
W = (185 kg)*(9.8 m/s²) = 1813 N

The normal reaction force on the piano from the floor is N = 1813 N, according to Newton's 3rd Law.

The coefficient of friction between the piano and the floor is given as μ = 0.39.

By definition, the frictional force is
F = μN 
   = 0.39*1813
   = 707.07 N

Answer: 707 N