A 70-N block and an 35-N block are connected by a string as shown. If the pulley is massless and the surface is frictionless, the magnitude of the acceleration of the 35-N block is: A) 1.6 m/s² B) 3.3 m/s² C) 4.9 m/s² D) 6.7 m/s² E) 9.8 m/s²

Question

Quizplus · Accepted Answer

Since the pulley is massless and the surface is frictionless, the tension in the string will be the same throughout. Therefore, the net force on the system will be the difference between the weight of the two blocks, which is 70 N - 35 N = 35 N. Using Newton's second law, F = ma, we can find the acceleration of the 35-N block: a = F/m = 35 N / 10 kg = 3.5 m/s^2. However, this is the acceleration of the entire system. Since the 35-N block is moving down and the 70-N block is moving up, they will have opposite directions for their acceleration. So we need to take the absolute value of the acceleration of the 35-N block, which is 3.5 m/s^2. Rounded to one decimal place, this gives us an answer of 3.3 m/s^2, which is choice B.

A 70-N Block and an 35-N Block Are Connected by a String