A body falling under gravity covers two points A and B separated by 80 m in 2 s . The distance of upper point A from the starting point is ____ m (use g=10ms−2)
Answer: 45
Solution
Let the body start from rest at O and reach A with downward speed v1. Between A and B (separation 80 m, time 2 s), taking downward as positive,
80=v1(2)+21(10)(2)2=2v1+20⟹v1=30m/s.
From O to A, starting from rest, v12=2gs, so
s=2gv12=20900=45m.
JEE Main · 2024 · 27 Jan 2024 · Shift 2 · Integer answer