There is head-on elastic collision between the two particles moving in the same direction with speeds $5 \mathrm{~m} / \mathrm{s}$ and $3 \mathrm{~m} / \mathrm{s}$ respectively. After collision, the velocity of the first particle becomes $4 \mathrm{~m} / \mathrm{s}$ in the same direction. The velocity of the second particle should be

When the heat is given to a gas in an Isothermal process, then there will be

An alternating voltage $\mathrm{E}=100 \sqrt{2} \sin (50 \mathrm{t})$ is connected to a $2 \mu \mathrm{~F}$ capacitor through an a.c. ammeter. The ammeter reading will be

In a Fraunhoffer diffraction, light of wavelength ' $\lambda$ ' is incident on slit of width ' d '. The diffraction pattern is observed on a screen placed at a distance ' $D$ '. The linear width of central maximum is equal to two times the width of the slit, then 'D' has value