The earth has a mass of `6 xx 10^(24)` kg and a radius of `6.4 xx 10^(6)m`. Calcualte the amount of work that must be done to slow down its rotation so that duration of day becomes 30 hrs instead of 24 hours.
Moment of inertia of earth = `(2)/(5)MR^(2).`

Find the mass of earth (Given the radius of earth R= 6.4 xx 10^6 m) .

If mass of Earth is 6xx10^24 kg, radius of Earth is 6.4 xx 10^6m and the gravitational constant is 6.7 xx10^-(11)Nm^2kg(-2) . Calculate the value of g.

The oxygen molecule has a mass of 5.30 xx 10^-26 kg and a moment of inertia of 1.94xx10^-46 kg m^2 about an axis through its centre perpendicular to the lines joining the two atoms. Suppose the mean speed of such a molecule in a gas is 500 m//s and that its kinetic energy of rotation is two thirds of its kinetic energy of translation. Find the average angular velocity of the molecule.

Calculate the strength of magnetic field due to an electron revolving in a circle of radius 2xx10^-10 m with a speed of 5xx10^6 ms^-1 at its centre.

In a hydrogen atom, electron moves in an orbit of radius 5xx10^(-11)m with a speed of 2.2xx10^(6)(m)/(s). Calculate the equivalent current.

A copper wire of resistivity 1.6xx10^-8 ohm-m has a cross sectional area of 20xx10^-4 cm^2 . Calculate the length of wire required to make a 10 ohm coil.