$A$ regular polygon of $n$ sides has $170$ diagonals,then $n$ is equal to

The energy $(E)$,angular momentum $(L)$,and universal gravitational constant $(G)$ are chosen as fundamental quantities. The dimensions of the universal gravitational constant in the dimensional formula of Planck's constant $(h)$ is

$A$ ball is dropped from a height of $20 \ m$ above the surface of water in a lake. The refractive index of water is $4/3$. $A$ fish inside the lake, in the line of fall of the ball, is looking at the ball. At an instant, when the ball is $12.8 \ m$ above the water surface, the fish sees the speed of the ball as ........ $m/s$ $[g = 10 \ m/s^2.]$

$A$ gaseous mixture consists of $16 \ g$ of helium and $16 \ g$ of oxygen. The ratio $\frac{C_p}{C_v}$ of the mixture is

Which of the following oxides is amphoteric?

The energy that should be added to an electron to reduce its de Broglie wavelength from $1 \ nm$ to $0.5 \ nm$ is