Q 11-05-145JEE MainJEE Main 2021 (18 Mar, Shift 2)Easy
A ball of mass 4 kg, moving with a velocity of $10\ \text{m s}^{-1}$, collides with a spring of length 8 m and force constant $100\ \text{N m}^{-1}$. The length of the compressed spring is $x$ m. The value of $x$, to the nearest integer, is ______.
Numerical value type. Enter your answer.
Answer: 6
All the kinetic energy is stored in the spring at maximum compression:
$$\frac12\times4\times10^2 = \frac12\times100\times d^2 \Rightarrow d = 2\ \text{m}$$
Compressed length $= 8 - 2 = 6$ m.
Solution by Sreeraj P, M.Sc Physics