Physics question involving pulley, tension, and coefficient of friction...?

Question

I'm stuck on a Physics problem-
A 7.5 kg block is resting on a horizontal surface, and is connected to a 5.50 kg mass suspended from a string passes over a frictionless pulley. Find the acceleration of the system and the tension in the string if the surface is:
(a)
smooth, and
(b)
the coefficient of friction is 0.190

I have found the acceleration of the system with the smooth surface, but i can't find the tension in the two strings or the acceleration of the system with the coefficient of friction.....

Any help is greatly appreciated.....

Answer 1

So in both a and b the force acting upon the 7.5kg block through the string is 5.5kg*g = 53.9N.

In part b, the friction is effectively reducing the force by 7.5kg*g*uf = 13.965N yielding 39.935 N effective force pulling the block.

about 5.3 m/s/s

I don't think there is any tension in part a and in part b the tension is about 14N

Answer 2

when you draw out your free body diagram for part b, it is the same as part A, but you will have a force in the oposite direction of the movement. then, before you figure out the acceleration, you can just subtract that negative force from the one that is causing the movement, then use f=ma, can't for the life of me remember the equation for force due to friction. I think it's the coefficient of friction*mass, but I may have left something out, double check me