A diver steps off a diving platform that is 10m above the water. If there is no air resistance during the fall, there will be a decrease in the diver's

Analyze the question: A diver falls freely from 10 m with no air resistance. Which quantity decreases during the fall?

Concept: In free fall without air resistance, only gravity does work, so mechanical energy is conserved:

• Gravitational potential energy (PE = mgh) depends on height. As the diver falls, h decreases, so PE decreases.
• Kinetic energy (KE = ½mv²) depends on speed. As the diver speeds up (v = gt), KE increases.
• Total mechanical energy (PE + KE) stays constant, since there is no air resistance to remove energy.
• Momentum (p = mv) increases because the velocity increases.

Step-by-step check of each option:

• A. Gravitational potential energy: decreases as the diver loses height (from mg(10) toward 0). ✔
• B. Total mechanical energy: constant, because energy is conserved. ✘
• C. Kinetic energy: increases. ✘
• D. Momentum: increases. ✘

Answer: The only quantity that decreases is the diver's gravitational potential energy.

Tip: In free fall (no air resistance), remember "PE goes down, KE goes up, total stays the same." When a question asks what decreases, look for the quantity tied to height. If air resistance were present, total mechanical energy would also decrease because some of it would be lost as heat.