Question

A uniform metre rule $AB$ is supported at its centre of gravity by a knife-edge. A force of $4N$ is applied at a point which is $20cm$ from end A of the rule. Calculate the force which must be applied to end B to restore the equilibrium of the rod

• A. 4 N
  
• B. 2.4 N
  
• C. 1.2 N
  
• D. 4.8 N
  

Answer 1

The correct option is B 2.4 N

For eqilibrium,

$4\times (50-20)=W\times 50$

$4\times 30=W\times 50$

$\Rightarrow W=\frac{12}{5}=2.4N$