Math Is Fun Forum

Two loads P and Q, of masses 2kg and 3kg respectively, are connected by a light inextensible string. Load P is on a rough horizontal table. The string passes over a smooth pulley fixed at the edge of the table, and load Q hangs vertically. A force of magnitude 30N acting at 30 degrees to the table is just sufficient to keep P in equilibrium. This force acts in the vertical plane containing the string.

Modelling the loads as particles, show that the coefficient of friction between P and the table is approximately 0.75.

The force of magnitude 30N is now removed. Ignoring air resistance, find the tension in the string in the ensuring motion.

Please help! Friction isn't one of my strong suits, and I'm having real trouble with this question!