Question

When a load of 10 kg is hung from the wire, then extension of 2 m is produced. Then work done by restoring force is

• A. 200 J
• B. 100 J
• C. 50 J
• D. 25 J

Answer 1

The correct option is B 100 J

We know$,$ restoring force is given by hook's law$.$

$e.g.$, restoring force $,F=kx$

and weight$=mg$

here restoring force is balanced by weight

so$,kx=mg$

$k=\left(mg/x\right)$

here m $=2kg,g=10m/s²andx=2m$

so$,$ k $=(10\times 10/2)=50N/m$

now $,$ workdone by restoring force $=1/2kx²$

$=1/2\times 50\times \left(2\right)²$

$=1/2\times 50\times 4$

$=100J$

Hence,

option $\left(B\right)$ is correct answer.