Question

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

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

Answer 1

The correct option is C

300 J

$100=\frac{1}{2}k{x}^2$ (given)

$W=\frac{1}{2}k(x_2^2-x_1^2)=\frac{1}{2}k\left[\right(2x{)}^2-x^2]$

$=3\times (\frac{1}{2}k{x}^2)=3\times 100=300J$