Question

Two blocks of mass m and M are hanging off a single pulley, as shown. Determine the acceleration of the blocks. Ignore the mass of the pulley. m = 1 kg and M = 2 kg, g= 10 $m/s^2$.

• A. 5/2
• B. 10/3
• C. 10
• D. 10/7

Answer 1

The correct option is B 10/3

Apply Newton's second law to the block on the right. We have Mg—T = Ma (taking the downward direction as positive). Apply Newton's second law to the block on the left. We have mg—T = -ma (the acceleration of the two blocks have opposite signs, since one moves up and the other moves down). Combine these two equations and we can find an expression for the acceleration of the blocks.

Answer: a = (M—m)g/(M+m)