A mass $$0.4 \mathrm{~kg}$$ performs S.H.M. with a frequency $$\frac{16}{\pi} \mathrm{Hz}$$. At a certain displacement it has kinetic energy $$2 \mathrm{~J}$$ and potential energy $$1.2 \mathrm{~J}$$. The amplitude of oscillation is

The mass of a planet is six times that of the earth. The radius of the planet is twice that of the earth. If the escape velocity from the earth is '$$V_e$$', then the escape velocity from the planet is

A biconvex lens $$\left(R_1=R_2=30 \mathrm{~cm}\right)$$ has focal length equal to the focal length of concave mirror. The radius of curvature of concave mirror is [Refractive index of material of lens $$=1.6$$ ]

In an a.c. circuit, a resistance R = 40 $$\Omega$$ and an inductance 'L' are connected in series. If the phase angle between voltage and current is 45$$^\circ$$, then the value of the inductive reactance is (tan 45$$^\circ$$ = 1)