Question

If the potential energy of a spring is V on stretching it by 2 cm, then its potential energy when it is stretched by 10 cm will be

• A. V/25
• B. 5V
• C. V/5
• D. 25V

Answer 1

Answer: (D)

25V

Answer 2

∴ $U \propto l ^ { 2 }$

$\frac { U _ { 2 } } { U _ { 1 } } = \left( \frac { l _ { 2 } } { l _ { 1 } } \right) ^ { 2 } = \left( \frac { 10 } { 2 } \right) ^ { 2 } = 25$⇒ $U _ { 2 } = 25 U _ { 1 }$

i.e. potential energy of the spring will be 25 V