A 3.0-kg and a 5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of 32 N is applied to the 5.0-kg box pushing it against the 3.0-kg box, and, as a result, both boxes slide along the floor. How hard do the two boxes push against each other?
A) 24 N
B) 0 N
C) 32 N
D) 12 N
E) 20 N

Question

A  3.0-kg and a  5.0-kg box rest side-by-side on a smooth, level floor. A horizontal force of  32 N is applied to the  5.0-kg box pushing it against the  3.0-kg box, and, as a result, both boxes slide along the floor. How hard do the two boxes push against each other?
A)  24 N
B)  0 N
C)  32 N
D)  12 N
E)  20 N

Quizplus · Accepted Answer

The force exerted by the 3.0-kg box on the 5.0-kg box is equal to the force needed to accelerate the 3.0-kg box. Using F = ma, the acceleration of the system is 32 N / (3.0 kg + 5.0 kg) = 4 m/s². The force on the 3.0-kg box is 3.0 kg * 4 m/s² = 12 N.

A 30-Kg and a 5