Question

A long string is stretched by $2\, cm$ and the potential energy is $V$. If the spring is stretched by $10\, cm$, its potential energy will be

• A. V/25
• B. V/5
• C. 5 V
• D. 25 V

Answer 1

Answer: (D)

25 V

Answer 2

$V=\frac{1}{2} k(x)^{2}=\frac{1}{2} k(2)^{2}$
or $k =\frac{2 V}{4}=\frac{V}{2}$
$V'=\frac{1}{2} k(10)^{2}=\frac{1}{2} \times\left(\frac{V}{2}\right)(10)^{2}$
$=25\, V$