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

Answer: (C)

300 J

Answer 2

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

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