Two equal masses are raised at constant velocity by ropes that run over pulleys, as shown below. Mass B is raised twice as fast as mass A. The magnitudes of the forces are F_A and F_B, while the power supplied is respectively P_A and P_B. Which statement is correct? A) F_B = F_A; P_B = P_A. B) F_B = F_A; P_B = 2 P_A. C) F_B = 2 F_A; P_B = P_A. D) F_B = 2 F_A; P_B = 2 P_A. E) P_A = F_A; P_B = F_B.

Question

Quizplus · Accepted Answer

Since mass B is raised twice as fast as mass A, the velocity of B is twice that of A. Therefore, the power supplied to raise B is twice that supplied to raise A (as work done = force x distance, and distance over time is velocity). However, the forces needed to raise the masses are equal since they are connected through the same rope and pulley system. Therefore, answer option B is correct where both forces are equal but the power supplied to raise B is twice that supplied to raise A.

Two Equal Masses Are Raised at Constant Velocity by Ropes