Calculating Pulley System Equilibrium: Solving for Maximum and Constant Velocity

[eddieT213]

Pulley Systems: HELP!

Hey guys so I'm trying to do this last question on the homework but I'm stumped and don't even know where to begin...Can someone please help me out?

Question:
Two masses are connected by a string that passes over a pulley. Mass#1 of 10kg is on a frictional surface with coefficients of static and kinetic friction of 0.8 and 0.5, respectively. (a) find the maximum weight of mass #2 before the system just barely wants to move. (b) Find the weight of mass #2 so that the system moves with a constant velocity.

 

[jbsteele]

Solution:a) The maximum weight of mass #2 before the system just barely wants to move is equal to the force of static friction. This force can be calculated using the formula F = μ * N, where μ is the coefficient of static friction and N is the normal force. Since we know the mass of mass #1, we can calculate the normal force using the equation N = m * g, where m is the mass and g is the acceleration due to gravity (9.8m/s^2). Therefore, the maximum weight of mass #2 is given by: F = μ * N = 0.8 * (10kg * 9.8m/s^2) = 78.4Nb) The weight of mass #2 so that the system moves with a constant velocity is equal to the force of kinetic friction. This force can be calculated using the formula F = μ * N, where μ is the coefficient of kinetic friction and N is the normal force. Using the same calculations as in part (a), the weight of mass #2 is given by: F = μ * N = 0.5 * (10kg * 9.8m/s^2) = 49N