A ball of mass 50 g falls from rest vertically downwards through a distance of 40 m and hits the ground. Find its kinetic energy and final velocity before it hits the ground (kinetic energy in J).
Physics · Mixed Chapter
JEE Main Practice

Question

A ball of mass 50 g falls from rest vertically downwards through a distance of 40 m and hits the ground. Find its kinetic energy and final velocity before it hits the ground (kinetic energy in J).

G1 Physics · Accepted Answer

Step 1: m = 50 g = 0.050 kg; h = 40 m. Take g = 9.8 m s⁻². Step 2: By mechanical energy conservation, K = mgh = 0.050 × 9.8 × 40 = 19.6 J. Step 3: From v² = u² + 2gh, v = √(2 × 9.8 × 40) = √784 = 28 m s⁻¹ downward. Final values: kinetic energy = 19.6 J; final speed = 28 m s⁻¹. Correct Answer column stores source's 19.6 J.