Which statement best defines kinetic energy?

Which statement best defines kinetic energy?

• A. The energy stored by a compressed spring.
• B. The energy of motion, i.e., the energy of a moving mass.
• C. The energy due to gravitational potential.
• D. The energy in a magnetic field.

Answer: (B)

The main idea tested is what kinetic energy represents. It is the energy an object has because it is moving—the energy of motion of a moving mass. The best definition is that kinetic energy is the energy of motion, which increases with both the mass and the speed of the object and is given by the formula KE = 1/2 m v^2. This means the energy grows as speed increases, and it changes when work is done on or by the object: speeding up transfers energy into kinetic energy, while slowing down converts that kinetic energy into other forms like heat or sound. The other descriptions refer to energy stored in a fixed state rather than in motion. Energy stored by a compressed spring is elastic potential energy, not kinetic. Gravitational potential energy is energy due to position in a gravitational field, and energy in a magnetic field is magnetic energy. These can become kinetic energy when conditions change (for example, gravitational potential energy turning into kinetic energy as something falls), but their primary definition is not energy of motion.

The main idea tested is what kinetic energy represents. It is the energy an object has because it is moving—the energy of motion of a moving mass. The best definition is that kinetic energy is the energy of motion, which increases with both the mass and the speed of the object and is given by the formula KE = 1/2 m v^2. This means the energy grows as speed increases, and it changes when work is done on or by the object: speeding up transfers energy into kinetic energy, while slowing down converts that kinetic energy into other forms like heat or sound.

The other descriptions refer to energy stored in a fixed state rather than in motion. Energy stored by a compressed spring is elastic potential energy, not kinetic. Gravitational potential energy is energy due to position in a gravitational field, and energy in a magnetic field is magnetic energy. These can become kinetic energy when conditions change (for example, gravitational potential energy turning into kinetic energy as something falls), but their primary definition is not energy of motion.