An object of mass 0.50 kg is released from rest at a height of 4.0 m. What is its kinetic energy just before it hits the ground (ignore air resistance)?

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Multiple Choice

An object of mass 0.50 kg is released from rest at a height of 4.0 m. What is its kinetic energy just before it hits the ground (ignore air resistance)?

The main idea is energy conservation when air resistance is ignored, so gravitational potential energy can be completely converted into kinetic energy as the object falls. At the start, the kinetic energy is zero because it is released from rest, and the potential energy is mgh = 0.50 × 9.8 × 4.0 = 19.6 joules. As it falls, this potential energy becomes kinetic energy. Just before hitting the ground, the height is zero, so all the energy is kinetic: KE = 19.6 J. Therefore, the kinetic energy just before impact is 19.6 J. The other numbers would require different heights or masses.

The main idea is energy conservation when air resistance is ignored, so gravitational potential energy can be completely converted into kinetic energy as the object falls.

At the start, the kinetic energy is zero because it is released from rest, and the potential energy is mgh = 0.50 × 9.8 × 4.0 = 19.6 joules. As it falls, this potential energy becomes kinetic energy. Just before hitting the ground, the height is zero, so all the energy is kinetic: KE = 19.6 J. Therefore, the kinetic energy just before impact is 19.6 J. The other numbers would require different heights or masses.

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