A person has a normal near point $$25 \mathrm{~cm}$$. What is the magnifying power of the simple microscope he used, if the focal length of the convex lens used is $$10 \mathrm{~cm}$$ and the final image is formed at the least distance of distinct vision?
If reaction is $$\mathrm{R}$$ and coefficient of friction is $$\mu$$, what is work done against friction in moving a body by distance $$\mathrm{d}$$ ?
The electric flux from cube of side $$1 \mathrm{~m}$$ is '$$\Phi$$' When the side of the cube is made $$3 \mathrm{~m}$$ and the charge enclosed by the cube is made one third of the original value, then the flux from the bigger cube will be :
An uniform sphere of mass $$M$$ and radius $$R$$ exerts a force of $$F$$ on a small mass $$m$$ placed at a distance of 3R from the centre of the sphere. A spherical portion of diameter $$R$$ is cut from the sphere as shown in the fig. The force of attraction between the remaining part of the disc and the mass $$\mathrm{m}$$ is