Question

When a spring is stretched by $2cm$, it stores $100J$ of energy. If it is stretched further by $2cm$, the stored energy will be increased by (in J)

• A. $100$
  
• B. $200$
  
• C. $300$
  
• D. $400$

Answer 1

The correct option is C $300$

Initial energy $=100=0.5\times k\times {0.02}^2$

$\Rightarrow k=50\times {10}^{4}N/m$

Final energy $=0.5\times 50\times {10}^4\times (0.02+0.02{)}^2=400J$

Increase in energy $=400-100=300J$

Hence correct answer is option $C$