Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100 N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same.Which of the figures below shows a correct free-body diagram of the horizontal forces acting on lower block,B?
E)None of these diagrams is correct.

Question

Quizplus · Accepted Answer

Block B experiences a normal force from the surface equal in magnitude and opposite in direction to its weight. Block A also experiences the same normal force from the surface. The tension force from the rope is transmitted through both blocks and is therefore the same magnitude for both blocks. Since both blocks are moving together at a constant velocity, the net force on block B must be zero. This means that the tension force from the rope must be equal in magnitude and opposite in direction to the frictional force on block B. Therefore, the correct free-body diagram for block B is shown in choice B, where the tension force from the rope is equal in magnitude and opposite in direction to the frictional force, and the normal force from the surface is equal in magnitude and opposite in direction to the weight of block B.

Two Blocks,A and B,are Being Pulled to the Right Along