Question

A neutral atom which is stationary at the origin in gravity-free space emits an α-particle (A) in the z-direction. The product atom is P. A uniform magnetic field exists in the x-direction. Disregard the electrostatic forces between A and P.

(a) A and P will move along circular paths of equal radii.

(b) A has greater time ** of rotation than P.

(c) A has greater kinetic energy than P.

(d) A and P will meet again somewhere in the yz plane.

Answer 1

Correct Answer is: (a, c, & d)

As momentum must be conserved, the two move in opposite directions with equal momenta (p).

mv = p = BQr.

Here, B and Q are also the same for the two.

∴ r is the same.

T = 2π (m/QB)

The two have the same Q and B, but mP > mA.

∴ TP> TA.

Kinetic energy = p2/2m.

The two have the same p, but mP > mA.

∴ EA > EP.