Question Detail
Question
An object does free fall and it takes 60m distance during last 2 seconds of its motion. Find the height it is dropped (g = 10 m/s²).
Correct Answer
Option C is the correct answer.
Detailed Explanation
Let total time be T. Distance in last 2 seconds = ½gT² - ½g(T-2)² = ½g[T² - (T² - 4T + 4)] = ½g(4T - 4) = 2g(T - 1). So 60 = 2×10×(T-1) = 20(T-1). Thus T-1 = 3, T = 4 s. Total height = ½gT² = ½×10×16 = 80 m.
Hint
Distance in last t seconds = total distance - distance in (T-t) seconds.