Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be

A) zero.
B) less than F but not zero.
C) equal to F.
D) greater than F.

Question

Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force

(of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be
Two bodies P and Q on a smooth horizontal surface are connected by a light cord. The mass of P is greater than that of Q. A horizontal force (of magnitude F) is applied to Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P will be A) zero. B) less than F but not zero. C) equal to F. D) greater than F.

A) zero. 
B) less than F but not zero. 
C) equal to F. 
D) greater than F.

Quizplus · Accepted Answer

Since the surface is smooth, there is no horizontal frictional force acting on either body. Thus, the only horizontal force on body P is the force exerted by the connecting cord. This force, by Newton's third law, is equal in magnitude but opposite in direction to the force exerted by body P on the cord. Since body P is more massive, it will experience a smaller acceleration than body Q. Therefore, the tension in the cord will be less than the applied force F but not zero. Thus, the correct answer is B: less than F but not zero.

Two Bodies P and Q on a Smooth Horizontal Surface