Final answer:
When a block hits an ideal spring, it compresses the spring and momentarily comes to rest before the spring pushes it back, causing it to bounce back with the same speed, assuming perfect elasticity and no energy losses.
Step-by-step explanation:
When a block of mass m traveling on a frictionless surface at speed v impacts an ideal spring, a few different outcomes are possible. If the question aligns with the typical physics of conservation of energy and momentum, then when the block hits the spring, it will compress the spring and eventually come to rest momentarily when the compression is maximized. After this, the spring will exert a force on the block, causing it to move in the opposite direction (as it wants to return to its equilibrium position). Therefore, based on energy conservation, the block will bounce back with the same speed, assuming a perfectly elastic collision and no energy losses, which corresponds to the outcome that the block bounces back with the same speed and the spring compresses.
The problem's descriptions involving blocks, springs, compression, and kinetic energy highlight crucial concepts in mechanics, specifically conservation of energy and momentum. Key calculations involve determining the compression of the spring as well as the potential energy stored in the spring and the kinetic energy of the blocks.
Regarding the initial question about the block and spring, option 3 would be the most accurate: the block bounces back with the same speed and the spring compresses.