Question

It is a common observation that rain clouds can be at about 1 km altitude above the ground. If a rain drop falls from such a height freely under gravity, then what will be its speed in km $h^{-1}$?

• A. 510
• B. 610
• C. 710
• D. 910

Answer 1

Answer: (B)

610

Here, $u=0,h=1km=1000m$

$g=10m/s^2$

Using $v^2-u^2=-2gh$

$v^2=2ghv=\sqrt{2gh}=\sqrt{2\times 10\times 1000}=141.4m{s}^{-1}=141.4\times \frac{18}{5}Km/h=509.04Km/h\approx 610km/h$