Question

A bead 'B' of mass m is attached to one end of a spring(AB) of natural length R and spring constant K= ($\sqrt{3}$+1)mg/R. The normal reaction at B just after it is released to move is:

• A.
• B. mg
• C. mg
• D. mg

Answer 1

The correct option is D

mg

Extension in the spring is

$x=AB-R=2Rcos{30}^{\circ }-R$

$=(\sqrt{3}-1)R$

Spring force

$F=kx=\frac{(\sqrt{3}+1)mg}{R}\times (\sqrt{3}-1)R$ = 2mg

From figure N = = (F + mg)cos ${30}^{\circ }$ = $\frac{\sqrt[x]{x3}mg}{2}$