Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure.The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N.What is the tension in wire A?
A) 87.5 N
B) 245 N
C) 280 N
D) 333 N
E) 517 N

Question

Three objects are connected by massless wires over a massless frictionless pulley as shown in the figure.The tension in the wire connecting the 10.0-kg and 15.0-kg objects is measured to be 133 N.What is the tension in wire A? 
A) 87.5 N 
B) 245 N 
C) 280 N 
D) 333 N 
E) 517 N

Quizplus · Accepted Answer

Using the free body diagram and considering the acceleration to be a constant g, we can write the following equations:

For the 10 kg block: 
T1 - 10g = -10a

For the 15 kg block: 
133 - T1 - 15g = 15a

For the 25 kg block: 
T2 - 25g = 25a

Since the pulley is massless and frictionless, the tension in all the wires will be the same.
Therefore, T2 = T1.

Solving these equations simultaneously, we get:
T1 = 333 N

Therefore, the tension in wire A is 333 N.

Three Objects Are Connected by Massless Wires Over a Massless