Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P.The tension in the wire is T (see figure).P is closest to
A) 25 N.
B) 125 N.
C) 187.5 N.
D) 245 N.
E) 1225 N.

Question

Two weights are connected by a massless wire and pulled upward with a constant speed of 1.50 m/s by a vertical pull P.The tension in the wire is T (see figure).P is closest to 
A) 25 N. 
B) 125 N. 
C) 187.5 N. 
D) 245 N. 
E) 1225 N.

Quizplus · Accepted Answer

Because the weights are being pulled upward at a constant speed, the net force on them must be zero. This means that the upward force P must be equal in magnitude to the weight of both weights combined. We can find this weight using the formula F = mg, where m is the mass and g is the acceleration due to gravity. The combined weight is:

F = (10 kg)(9.81 m/s²) + (5 kg)(9.81 m/s²) = 147.15 N

Since the net force is zero, the tension T in the wire must also be equal to 147.15 N. Therefore, P must also be equal to 147.15 N, since it is the only other force acting on the system. The answer closest to this value is B, 125 N.

Two Weights Are Connected by a Massless Wire and Pulled