Question

If the force constant of the spring is $50\text{N/m}$. Find the mass of the block if it rests in the given situation. Take $g=10m/s^2$

• A. $10\text{kg}$
• B. $20\text{kg}$
• C. $30\text{kg}$
• D. $40\text{kg}$

Answer 1

The correct option is A $10\text{kg}$

The FBD of spring and block of mass $m$ is as shown


for equilibrium condition, we have
$100=kx$ and $kx=mg$
$\Rightarrow 100=\text{mg}\Rightarrow m=10\text{kg}$

(OR)

The given arrangement of spring system can easily be converted to string system as shown.

where tension $T=kx$
So, from the FBDs we have
$T=mg$ and, $T=100$
$\Rightarrow mg=100$
$\therefore$ the equivalent mass is equal to $\frac{100}{g}=\frac{100}{10}=10kg$