JEE Mains · Physics · STD 11 - Motion in straight line
- JEE Mains 2026
- Easy
- MCQ
Water drops fall from a tap on the floor, 5 m below, at regular intervals of time, the first drop strikes the floor when the sixth drop begins to fall. The height at which the fourth drop will be from ground, at the instant when the first drop strikes the ground is ___________ m.
\(\left( g =10 m / s ^2\right)\)
Pick an option to check your answer.
Answer & Solution
Correct Answer
(C) 4.2
Step-by-step Solution
Detailed explanation
Time to reach ground \(= \sqrt{\frac{2h}{g}} = \sqrt{\frac{2 \times 5}{10}} = 1 sec\)
Five drops per second
Time between each drop \(= 0.2\ sec.\)
Time of fall for \(4^th\) drop is \(1 - 0.6 = 0.4\ sec\)
Height fall of \(4^th\) drop is \(= \frac{1}{2} \times 10 \times 0.4^{2} = 0.8 m\)
Height from ground \(= 5 - 0.8 = 4.2\ m\)
Five drops per second
Time between each drop \(= 0.2\ sec.\)
Time of fall for \(4^th\) drop is \(1 - 0.6 = 0.4\ sec\)
Height fall of \(4^th\) drop is \(= \frac{1}{2} \times 10 \times 0.4^{2} = 0.8 m\)
Height from ground \(= 5 - 0.8 = 4.2\ m\)
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