Hope you have gone through the first part of this tutorial where we have discussed the important points you need to remember while solving numerical problems from the FRICTION chapter. Also, we solved two simple but conceptual numerical there.
Three additional problems are listed there at the end under set 2. And, we are going to solve those numerical problems (given under set 2) now.
Set 2 solution (friction numerical set 2)
Problem i) A 52 N sled is pulled across a cement sidewalk at a constant speed. A horizontal force of 36 N is exerted. What is the coefficient of sliding friction between the sidewalk and the metal runners of the sled?
Weight of the sled = 52 N. Here the normal force on the slade = FN (sled) = 52 N
Hence the friction working against its motion = FF= μFN = μ 52 = 52μ (here μ is the coefficient of sliding friction between the sidewalk and the metal runners of the sled)
As the sled is moving at a constant speed that means the net force on it is zero. This implies that the horizontal force of 36 N on it just equals the friction in magnitude.
Hence, 52μ = 36
=> μ = 36/52 = 0.69
[ solution of other 2 problems are given in next 2 pages. Use the links below ]