Particle in a magnetic field -- question

[Cyclone Charlie]

Homework Statement

Question: An alpha particle (a He nucleus, containing two protons
and two neutrons and having a mass of 6.64 * 10-27 kg) traveling
horizontally at 35.6 km/s enters a uniform, vertical, 1.80-T magnetic field.
(a) What is the diameter of the path followed by this alpha particle?

Relevant Equations

R=mv/qb

I went with R=mv/qb, thus -> 6.64e-27*35.6e3/2*1.6e-19*1.8, and got 4.1e-4 m (metres), so diameter is 2R, 8.2e-4 m, as an answer, the reference site gives 3.95e+10 m as the answer, who's right here?

 

[kuruman]

Hi Cyclone Charlie and welcome to PF.

the reference site gives 3.95e+10 as the answer, who's right here?

3.95e+10 what? Apples, bananas, oranges? Without units a number is meaningless unless it is dimensionless, which in this case it cannot be. Same with your answer of 4.1e-4, meaningless. It is not possible to tell who is right and who is not.

 

[Cyclone Charlie]

Sorry Kuruman, forgot the units, the answer for the diameter is in metres.

 

[kuruman]

OK, do you think that the answer of 4 e+10 m for the diameter is realistic? That's about one-quarter the Sun-Earth distance. I cannot speak for your reference and how they got the absurd answer, but your answer is correct. Theirs must be a typo.