Out of the following musical instruments which is ' NOT ' a percussion instrument?

The enclosed air inside a closed box of rigid walls has pressure $P_1$. The density of air inside this box is constant. On heating the gas, the pressure of the enclosed air is increased from $P_1$ to $P_2$. Now it is observed that the sound travels $1.4$ times faster than at pressure $P_1$. The ratio $P_2$ by $P_1$ is

Select the WRONG statement about polar molecules.

An electric dipole of length $3\text{cm}$ is placed with its axis making an angle of $60^\circ$ with a uniform electric field of $5 \times 10^4$ N/C. It experiences a torque of $9\sqrt{3}$ Nm. The magnitude of charge on the dipole is $(\sin 60^\circ = \dfrac{\sqrt{3}}{2})$