A body of mass m is held against a vertical wall by a force p the direction of which is inclined to the vertical by an angle. Find the coefficient of friction
Answers
When the body is on the table top parallel to the ground the force of friction is equal to μ *N *cos θ where μ is the coefficient of friction N is the normal force and θ is 0 degrees. The formula is reduced to μ * N * 1 or friction = μ * N where N = W.
Your question is about a body pushed against a vertical wall. N in this case is 0 because the cosine of 90 degrees is 0. To provide the force of friction you push the block to act as the normal force since friction at 90 degrees is 0. In symbols F = μ * W
Usually in most surfaces μ is always less than 1. Let us assign μ= 0.6 for concrete wall and block of wood held against it.
F = 0.6 * W and if the weight is 20 newtons you will exert a 12 newtons force to hold it.
Generally, the force needed to hold the block is the product of the coefficient of friction times the weight of the block.