Alpha particles, each having a charge of +2e and a mass of 6.64 ×10-27 kg, are accelerated in a uniform 0.50 T magnetic field to a final orbit radius of 0.50 m. The field is perpendicular to the velocity of the particles. What is the kinetic energy of an alpha particle in the final orbit? (1 eV = 1.60 × 10-19 J, e = 1.60 × 10-19 C)

Explanation:

Given:

During the motion of a charge the magnetic force and the centripetal forces are balanced:

where:

v = velocity of the alpha particle

Here we observe that the velocity of the aprticle is close to the velocity of light. So the kinetic energy will be relativistic.

We firstly find the relativistic mass as:

now kinetic energy:

v 154.9= 0.9 length length s little over 154.9cm

i think the answer would be b