In an electron gun the potential difference between the filament and plate is $$4000 \mathrm{~V}$$. What will be the velocity of electron emitting from the gain?
A man of mass $m$ starts falling towards a planet of mass $$M$$ and radius $$R$$. As he reaches near to the surface, he realizes that will pass through a small role in the planet. As he enters the role, we sees that the planet is really made of two pieces a spherical shell of negligible thickness of mass $$3 M / 4$$ and a point mass $$M / 4$$ at the centre. Change in the force of gravity experienced by the man is
A vessel containing 1 mole of $$\mathrm{O}_2$$ gas (molar mass 32) at temperature $$T$$. The pressure of the gas is $$p$$. An identical vessel containing one mole of He gas (molar mass 4) at temperature $$4 T$$ has a pressure of
The fundamental frequency of an open organ pipe is $$600 \mathrm{~Hz}$$. The first overtone of this pipe has same frequency as first overtone of a closed organ pipe. If speed of sound is $$330 \mathrm{~m} / \mathrm{s}$$, then the length of a closed organ pipe is