The flow speeds of air on the lower and upper surfaces of the wing of an aeroplane are $v$ and $2v$ respectively. The density of air is $\rho $ and surface area of wing is $A$ . The dynamic lift on the wing is
$\frac{1}{2}\rho {v^2}\,A$
$\rho {v^2}\,A$
$\frac{3}{2}\rho {v^2}\,A$
$2\rho {v^2}\,A$
Why free surface of liquid tend to contract their surface ?
Scent sprayer is based on
The pressure of water in a water pipe when tap is opened and closed is respectively $3 \times 10^5\,N/m^2$ and $3.5 \times 10^5\,N/m^2$ . With open tap, the velocity of water flowing is ........... $m/s$
Why is it dangerous to stand on the edge of platform near the line, when the train is passing with speed ? Explain.
What is a venturi-meter ? Explain its construction and working.