If a particle of charge q is moving with velocity `vecv` along y axis and a magnetic field `vecb` act along z axis, find the force acting on it. What happens to its kinetic energy ? Justify.

Explanation

`vecv= vecj v, vecB = veck B`
`:. vecF= q vecv xx vec B =q( vec jxx veck) vB= veci q vB`
`vecv and vecF` are mutually pependicular. So the magnetic force does not change the magnitude of the particle velocity i.e., the kinetic energy of the particle would remain unchanged.