# Alpha, beta particle radius of curviture

1. Sep 29, 2010

### pat666

1. The problem statement, all variables and given/known data

see attachment

2. Relevant equations

r=RoA1/3
Ro=1.2*10-15
3. The attempt at a solution

35 kiloelectron volts = 5.60761762 × 10-15 joules

I could calculate the velocity if I knew mass but that wouldn't help with the radius?
I think that I need to find A from the energy but how do I do that?

#### Attached Files:

• ###### rcurv.jpg
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2. Sep 30, 2010

### rl.bhat

The relevant equations are

mv^2/r = qvB. Or

mv = qrB.

sqrt(2mE) = qrB. where E is the energy of the particle , m is the mass of the particle.

Mass of β particle is the mass of the electron and mass of the α particle is equal to 4 times the mass of the proton.

3. Sep 30, 2010

### pat666

Hey,
thanks that worked for the beta particle but not the alpha particle.
sqrt(2*4*1.6726E-27*5.61E-15)=1.602E-19*r*1.1 then I solved that and got 0.05m and thats wrong!

theres a similar Question in the text book but the energy is 40keV and B=1.5T the answer in the text book for the alpha particle is 19.3mm and when I try it I get 0.0525m???

thanks for helping!

4. Sep 30, 2010

### rl.bhat

For alpha particle q = 2*e = 2*1.6*10^-19 C.

5. Sep 30, 2010

### pat666

Thanks heaps - problem solved!