What is the acceleration of a proton moving with a speed of 7.0 m/s at right angles to a magnetic field of 1.7 t?

We know that a charge moving in a magnetic field is subject to the force:

F = q · v · B

But we also know that:

F = m · a

Therefore, it must be:

m · a = q · v · B

And solving for a:

a = q · v · B / m

Recall that for a proton:

q = 1.6 * 10⁻¹⁹ C

m = 1.673*10⁻²⁷ kg

Now, you can find:

a = 1.6*10⁻¹⁹ · 7.0 · 1.7 / 1.673*10⁻²⁷

= 1.14 * 10⁹ m/s²

Hence, the acceleration of the proton is 1.14 * 10⁹ m/s².