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?

Sand falls vertically on a conveyor belt at a work rate of 0⋅1 kg/s. In order to keep the belt moving at a uniform speed of 2 m/s, the force required to be applied on the belt is :