# Physics

posted by
**Jeanne**
.

Two boxes on a horizontal surface, as shown in the figure above, are moving together under the influence of a horizontal force, F. The coefficient of kinetic friction between the boxes and the surface is 0.40. Use g = 10 m/s2. In case (a), a horizontal force F directed right is applied to the larger box, which has a mass of 8.00 kg. In case (b), the horizontal force F is instead applied to the smaller box, which has a mass of 4.00 kg. The horizontal force F has a magnitude of 110. N.

(a) Let's say that the boxes are moving to the right, in the direction of the force F. What is the magnitude of the force exerted by the larger box on the smaller box in:

(i) case (a)

(N)

(ii) case (b)

(N)

(b) Now, consider the case in which the boxes are initially moving to the left, opposite to the direction of the force F.

(i) For case (a), what is the magnitude of the acceleration of the system?

(N)

(ii) For case (a), what is the magnitude of the force applied by the larger box on the smaller box?

(N )