A 0.4 kg mass takes 8 s to reach ground when dropped from a certain height P above surface of earth. The loss of potential energy in the last second of fall is ____ J. [Take g = 10 m s⁻²]
Physics · Circular Motion
JEE Mains 29 January 2023 Shift 1 Morning Shift

Question

A 0.4 kg mass takes 8 s to reach ground when dropped from a certain height P above surface of earth. The loss of potential energy in the last second of fall is ____ J. [Take g = 10 m s⁻²]

G1 Physics · Accepted Answer

Distance covered in the 8th second for free fall from rest is s₈ = (g/2)(2×8−1) = 5×15 = 75 m. Loss of potential energy = mgs₈ = 0.4×10×75 = 300 J.