A 5 kg block is raised to a height of 2 m and then released. It falls and compresses a spring with spring constant 200 N m⁻¹ by 0.3 m. Assume no friction or air resistance. Explain the energy changes that take place from the moment the block is raised to the moment the spring is fully compressed.

1. The block has gravitational potential energy mgh = 5 kg × 9.8 m s⁻² × 2 m = 98 J before it is released.
2. As it falls, this potential energy is converted into kinetic energy; at the bottom of the fall the kinetic energy equals the initial 98 J.
3. When the block compresses the spring, the kinetic energy is transferred into elastic potential energy of the spring, which is ½kx² = ½ × 200 N m⁻¹ × (0.3 m)² = 9 J.
4. Energy is conserved: the total mechanical energy (98 J) remains constant (ignoring friction), so the remaining energy is stored as elastic potential energy in the spring.