Question

If a charged particle moves through a region of
magnetic field pointing in the direction
perpendicular to its direction of velocity. Then
during its subsequent motion,
(1) Its momentum changes but the kinetic
energy remains constant
(2) Its momentum and kinetic energy both
changes.
(3) Its momentum and kinetic energy both
remains constant.
(4) Its kinetic energy changes but the
momentum remains constant.

Answer 1

(1) Its momentum changes but the kinetic
energy remains constant.

This is because particle get deflected & move in a curved path so the velocity changes as the direction of the speed changes hence the movement on the body also changes while the kinetic energy remains constant.

Answer 2

hey there,

we know that when charge particle is moving in magnetic field and if magnetic field is perpendicular to the direction of velocity then particle moves in a circular path.

we know that work done in moving a charge particle in circular path is zero

=) so from work energy theorem ,

work done = change in kinetic energy

here, work done = 0

so change in K.E = 0

=). Kf - Ki = 0

=). Kf = Ki

final kinetic energy = initial kinetic energy

no change in kinetic energy .

I.e kinetic energy remains constant.

◆ now on moving in a circular path velocity changes at every instant

so momentum (p) = mv

so if velocity changes then momentum also changes..

so correct option us:-

kinetic energy remains constant but momentum changes.

______________________________

hope it will help u