Question

Water drops fall at regular intervals from a tap which is 5m above the ground. The third drop is leaving the tap at the instant the first drop touches the ground. How far above the ground is the second drop at that instant

• A. 2.50 m
• B. 3.75 m
• C. 4.00 m
• D. 1.25 m

Answer 1

The correct option is C 3.75 m
Height from ground = 5m

Time taken by first drop to reach the ground $t=\sqrt{\frac{2h}{g}}$

$t=\sqrt{\frac{2\times 5}{10}}$
⇒ t = 1sec
The third drop is leaving the tap at the instant the first drop touches the ground. As the water drops fall at regular intervals from a tap therefore time difference between any two drops is1/2 sec
In this given time, distance of second drop from the tap is

$s=ut+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.\times a\times t^2$

$s=0+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.\times g\times t^2$

$s=0+\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$2$}\right.\times 10\times {\left(\frac{1}{2}\right)}^2$

s =1.25 m
The distance from the ground = 5-1.25=3.75 m