A body takes 4 min. to cool from 61$$^\circ$$ C to 59$$^\circ$$ C. If the temperature of the surroundings is 30$$^\circ$$ C, the time taken by the body to cool from 51$$^\circ$$ C to 49$$^\circ$$ C is :

Consider an electrical circuit containing a two way switch 'S'. Initially S is open and then T₁ is connected to T₂. As the current in R = 6$$\Omega$$ attains a maximum value of steady state level, T₁ is disconnected from T₂ and immediately connected to T₃. Potential drop across r = 3$$\Omega$$ resistor immediately after T₁ is connected to T₃ is __________ V. (Round off to the Nearest Integer)

Suppose two planets (spherical in shape) in radii R and 2R, but mass M and 9M respectively have a centre to centre separation 8 R as shown in the figure. A satellite of mass 'm' is projected from the surface of the planet of mass 'M' directly towards the centre of the second planet. The minimum speed 'v' required for the satellite to reach the surface of the second planet is $$\sqrt {{a \over 7}{{GM} \over R}} $$ then the value of 'a' is ____________.

[Given : The two planets are fixed in their position]

In Bohr's atomic model, the electron is assumed to revolve in a circular orbit of radius 0.5 $$\mathop A\limits^o $$. If the speed of electron is 2.2 $$\times$$ 16⁶ m/s, then the current associated with the electron will be _____________ $$\times$$ 10^$$-$$2 mA. [Take $$\pi$$ as $${{22} \over 7}$$]