Which of the following halogen oxides is ionic?

$A$ circular disc of radius $R$ and thickness $\frac{R}{6}$ has moment of inertia $I$ about an axis passing through its centre and perpendicular to its plane. It is melted and recasted into a solid sphere. The moment of inertia of the sphere about its diameter as axis of rotation is

The correct order of second $I.E.$ of $C, N, O$ and $F$ is:

Which of the following is not a synthetic polymer?

When a capacitor is connected in series to an $LR$ circuit,the alternating current flowing in the circuit

$A$ cup of tea cools from $80^{\circ}C$ to $60^{\circ}C$ in $1$ minute. The ambient temperature is $30^{\circ}C$. How many seconds will it take to cool from $60^{\circ}C$ to $50^{\circ}C$?