A Level Physics Practice Exam

Why does the velocity of a diver not depend on mass when diving from a height with negligible air resistance?

1. All potential energy is converted to kinetic energy

2. Air resistance adds to kinetic energy

3. Mass affects gravitational potential energy differently

4. The kinetic energy is lost as heat

The correct answer is: All potential energy is converted to kinetic energy

The correct interpretation of why the velocity of a diver does not depend on mass when diving from a height with negligible air resistance is rooted in the conservation of energy. Specifically, when a diver jumps from a height, the potential energy they possess at the top of their dive is converted into kinetic energy as they fall. In the absence of air resistance, all of the gravitational potential energy the diver has at the beginning is transformed into kinetic energy just before reaching the water. The key point here is that gravitational potential energy and kinetic energy are both directly related to mass. However, when considering the velocity of the diver, the mass cancels out during the calculation of energy transformation. Using the principle of conservation of mechanical energy, we can express this as: \[ mgh = \frac{1}{2} mv^2 \] In this equation, m (mass) appears on both sides, and when solving for the final velocity (v), the mass cancels out, indicating that the final velocity is independent of the mass of the diver. This fundamental principle is crucial in understanding why mass does not affect the speed upon hitting the water, highlighting the nature of gravitational acceleration that acts equally on all objects regardless of their mass when air resistance is negligible.