Question

The potential energy of a long spring when stretched by 2 cm is U. If the spring is stretched by 8 cm the potential energy stored in it is:

• A. 4U
• B. $\frac U8$
• C. 16U
• D. $\frac U4$

Answer 1

Answer: (C)

16U

Answer 2

$U = \frac 12K(2)^2 = 2K$

$U' = \frac 12K(8)^2 = 32K$

Now,

$\frac {U'}{U} = \frac {32K}{2K}$

$\frac {U'}{U} = 16$

$U' = 16U$

So, the correct option is (C): 16U