A Level Physics Practice Exam

How does air resistance impact the kinetic energy of a falling object?

1. It decreases the kinetic energy

2. It increases the kinetic energy

3. It has no effect on the kinetic energy

4. It converts kinetic energy to gravitational potential energy

The correct answer is: It decreases the kinetic energy

Air resistance, also known as drag, acts in the opposite direction to the motion of a falling object. As the object falls, its velocity increases, and so does the force of air resistance acting against it. The work done by air resistance takes energy away from the falling object, meaning that as it falls, not all of the energy it gains from gravitational potential energy is converted into kinetic energy. When an object falls under the influence of gravity without air resistance, all of its potential energy would be converted to kinetic energy as it descends. However, due to air resistance, some of the energy is dissipated as thermal energy (heat), which means that less kinetic energy is available. As a result, the actual kinetic energy of the object when it hits the ground will be lower than it would be without air resistance. This reduction in kinetic energy is why air resistance is said to decrease the kinetic energy of a falling object.