JEE MainPhysicsMotion in A Straight LineMCQ+4 / −1
A parachutist after bailing out falls without friction. When parachute opens, it decelerates at He reaches the ground with a speed of . At what height, did he bail out?
- A
- B
- C
- D
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Correct answer: D
- First phase: free fall for
The parachutist starts from rest and falls freely without air resistance for .
Using with we get so the speed just before opening the parachute is
- Second phase: motion with parachute open
After the parachute opens, the parachutist is decelerated at (taking downward as positive, retardation means acceleration upward, hence negative).
He reaches the ground with speed
Let the distance covered after the parachute opens be .
Again use where
Thus,
- Total height from which he bailed out
Total height
This is closest to
Hence the correct option is D.
- Note on approximation
If one uses , the result is
So with the standard precise value , the answer is exactly option D.
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