# Conceptual physics question on tension

Jimmy1234

## Homework Statement

The hand in the figure is pushing on the back of block A. Blocks A and B, with mass B > mass A, are connected by a massless string and slide on a frictionless surface.

Is the force of the string on B larger than, smaller than, or equal to the force of the hand on A?

Picture: http://img713.imageshack.us/img713/1030/physicsq.jpg [Broken]

## The Attempt at a Solution

From my free body diagram, block B has a tension towards the right that should be less than the force applied to block A as they both move with the same acceleration.

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Mentor
Consider the forces on block A.

Jimmy1234
Block A has a force to the right and tension in the opposing direction. Because of conservation of string, the tension should be the same for Block B? Since this is on a frictionless surface, nothing is opposing the force applied on A so there will be an acceleration to the right meaning tension should be less than the force?

Mentor
I'd state it this way: The only forces on block A are the applied force and the string tension. The the blocks accelerate, so there must be a net force on A, thus the applied force must be greater than the tension. (And the tension is the same throughout a massless rope.)

Jimmy1234
Thank you! This thread can be closed.