A body of mass $m$ moving with velocity $v$ collides with a system of 2 blocks of each mass $m$ connected by a spring of spring constant $k$. All the three lie on the same plane (1D collision). There is no friction anywhere.Do the spring compress? . If yes then why? To compress or elongate a spring equal and opposite forces should be applied to opposite ends, then how could the spring compress. Please explain
[Physics] Collision of block and a spring system kept at rest
collisionconservation-lawsnewtonian-mechanicsspring
Best Answer
It seems you tacitly set a colinear collision, if not let me know to modify the answer.
The spring will compress in a variety of modes.
-If the collision is elastic, the moving block will stop entirely after it hits the stationary block and give all its momentum (Newtons system of balls and cradle ) to stationary block and then that stationary block starts to move back with speed v and this will compress the spring and start to push the last block back. This will start a free vibration in the system of the spring and two blocks which will gradually slide away while vibrating.
-If the collusion is not elastic there will be some loss of kinetic energy of the moving block and it may recoil back while pushing the second block back and compressing the spring, or depending on the stiffness and length of spring it may become one with the two blocks and move and with them at least for the compression part of the vibration.