Question

Two blocks of masses \(3kg\) and \(1kg\) are placed on a smooth horizontal surface. A horizontal force of \(5N\) acts on the system. Find the contact force between the two blocks.

• A. \(0\,N\)
• B. \(5\,N\)
• C. \(3.75\,N\)
• D. \(1.25\,N\)

Hint:

First calculate the common acceleration of the complete system and then isolate one block to determine the contact force.

Answer 1

The Correct Option is D

Step 1: Find acceleration of the system. Total mass \[ M=3+1=4kg \] \[ a=\frac{F}{M} \] \[ a=\frac{5}{4} \] \[ a=1.25m/s^2 \]

Step 2: Determine contact force. The contact force accelerates the \(1kg\) block. \[ N=ma \] \[ N=1\times1.25 \] \[ N=1.25N \] Final Answer: \[ \boxed{1.25N} \] Hence option \[ \boxed{(D)} \]