posted by Anonymous .
The figure shows a block P on top of another block Q. The two blocks are connected by a string which passes over a fixed smooth pulley. The mass of P is 0.20 kg and the mass of Q is 0.50 kg. The coefficient of static friction between blocks P and Q is 0.5 and between Q and the floor is 0.2. What is the maximum horizontal force F which can be applied before relative motion occurs between block Q and the floor. (3.335N)
The foecr balance three forces:
a. max friction between Q and floor F1=(0.5+0.2)*0.2*9.8
b. max friction between Q and P F2=0.2*0.5*9.8
c. max string tension F3=F2
finally F=F1+F2+F3=0.34*9.8=3.3 N