Static frictional coefficients are used for objects without relative motion. This is a very simplistic statement and quite misleading for brake materials. Calculate N, the normal force is the weight of the block. Drill a small starter hole into the side of the piece of wood. The stop distance is not dependent on the mass of the car. Start the block as far from the pulley as possible, release the block, and record the time, t, it takes to move a distance, L, along the track. The Physics Classroom: Kinematic Equations and Problem-Solving. lessons in math, English, science, history, and more. 'The first thing we do is, what?' The calculation for each scenario should be the reading off of the spring scale divided by the weight of the block of wood. What is the coefficient of friction for each scenario? © copyright 2003-2020 Study.com. just create an account. credit by exam that is accepted by over 1,500 colleges and universities. Where F k is the force of kinetic friction, μ k is the coefficient of sliding friction (or kinetic friction) and F n is the normal force, equal to the object’s weight if the problem involves a horizontal surface and no other vertical forces are acting (i.e., F n = mg, where m is the object’s mass and g is the acceleration due to gravity). Mathematically, μ = F / N, where F is the frictional force and N is the normal force.