Answer to Question #107140 in Classical Mechanics for Joseph

Question

A 750 g block can slide uniformly along the horizontal track when a string attached to it has the other end passed through a pulley with added mass of 180 g. What is the friction force between the block and the track?

A. 1.76 N
B. 7.35 N
C. 0.42 N
D.423.36 N

Answer 1

The friction force is equal to weight of added mass

$$F_f=W=mg=0.180\:\rm kg\times 9.8\: N/kg=1.76\: N.$$