Elastic Bounce: Temporary Conversion of Kinetic Energy

Steps:

• Ball approaches surface with downward velocity, possessing kinetic energy KE = ½mv².
• Upon contact, deformation stores KE as elastic potential energy in the ball.
• At maximum compression, velocity reaches zero, so KE drops to zero.
• Potential energy then releases, restoring original KE with reversed velocity.

Why B is correct:

• In an elastic collision, mechanical energy is conserved (no dissipation); KE converts to potential energy and back, hitting zero momentarily per conservation laws.

Why the others are wrong:

• A: Describes inelastic collision where energy dissipates as heat/sound, not elastic.
• C: KE varies during contact due to energy conversion, despite overall conservation.
• D: KE magnitude changes temporarily to zero; direction applies to velocity, not energy.

Final answer: B