A railway wagon (open at the top) of mass M₁ is moving with speed v₁ along a straight track. As a result of rain, after some time it gets partially filled with water so that the mass of the wagon becomes M₂ and speed becomes v₂. Taking the rain to be falling vertically and the water stationery inside the wagon, the relation between the two speeds v₁ and v₂ is :

Which one of the following statements is not true for a flute, a musical instrument?

A positive charge is moving towards south in a space where magnetic field is pointing in the north direction. The moving charge will experience :

Which one of the following astronomers proved that the Earth and other planets revolve around the Sun?