Rockets can move in airfree space but jet planes cannot. Why?

Light can travel in vacumm but sound cannot. Why?

Explain why moist chlorine can bleach dry coloured articles but dry chlorine cannot.

Removal of gonads cannot be considered as a contraceptive option. Why?

Write 'True' or 'Fasle': Sonic booms are caused by jet planes.

A particle with charge q moving with a velocity v in the plane of the paper enters a uniform magnetc field B, acting perpendicular to the plane of the paper. Deduce an expression for the tie period of the charge, as it moves in a circular path in the field. Why does the kinetic energy of the charge not change, while moving in the magnetic field?

The angle of elevation of a jet plane from a point A on the ground is 60^@ . After a flight of 15 secondsthe angle of elevation changes to 30^@ . If the jet plane is flying at a constant height of 1500sqrt3m , find the speed of the jet plane.