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

Since the system is moving at a constant speed, the net force on it must be zero. Therefore, the upward force provided by P must be equal to the combined weight of the two masses, which is 50 kg * 9.8 m/s^2 = 490 N.

Since the tension in the wire is the same throughout the entire length of the wire, it must also be equal to 490 N. Therefore, the answer is B) 125 N, which is the closest choice to 490 N.

Two Weights Are Connected by a Massless Wire and Pulled