2) A police car with a siren of frequency 8kHz is moving with uniform velocity 36km/hr towards a tall building which reflects the sound waves. The speed of sound in air is 320 m/s. The frequency of the siren heard by the car driver is

3) An electron and a proton are moving on straight parallel paths with same velocity. They enter a semi-infinite region of uniform magnetic field perpendicular to the velocity. Which of the following statement(s) is/are true ?

4) A spherical metal shell A of radius R_A and a solid metal sphere B of radius R_B(< R_A) are kept far apart and each is given charge ’+Q’. Now they are connected by a thin metal wire.Then

5) A dense collection of equal number of electrons and positive ions is called neutral plasma. Certain solids containing fixed positive ions surrounded by free electrons can be treated as neutral plasma. Let ’?N’ be the number density of free electrons, each of mass ’?m’. When the electrons are subjected to an to electric field, they are displaced relatively away from the heavy positive ions. If the electric field becomes zero, the electrons begin to oscillate about the positive ions wi

6) A dense collection of equal number of electrons and positive ions is called neutral plasma. Certain solids containing fixed positive ions surrounded by free electrons can be treated as neutral plasma. Let ’N’ be the number density of free electrons, each of mass ’?m’. When the electrons are subjected to an to electric field, they are displaced relatively away from the heavy positive ions. If the electric field becomes zero, the electrons begin to oscillate about the positive ions with