Question

A block of mass 2 kg collides with a horizontal mass-spring of force constant 2 Nm${}^{-1}$.The block compresses spring 4 m from the rest position. Speed of the block at instant of collision is

• A. 16 m/s
• B. 4 m/s
• C. 8 m/s
• D. 12 m/s

Answer 1

The correct option is B 4 m/s

We know,

Loss in $KE=$ gain in $PE$

$\frac{1}{2}\left(2\right)(v{)}^2=\frac{1}{2}K{x}^2$

$V^2=\frac{1}{2}\left(2\right)(v{)}^2$

$V=4m/s$