An alpha particle carries a charge of 3.2 × 10^–19 C. It experiences a force of 6.5 × 10^–14 N as it moves at a right angle through a magnetic field that has a magnitude of 1.4 × 10^–3 T. How fast is the particle moving?

2.9 × 10^-35 m/s
1.5 × 10^-35 m/s
1.5 × 10^8 m/s
2.8 × 10^8 m/s

Question

An alpha particle carries a charge of 3.2 × 10^–19 C. It experiences a force of 6.5 × 10^–14 N as it moves at a right angle through a magnetic field that has a magnitude of 1.4 × 10^–3 T. How fast is the particle moving?

2.9 × 10^-35 m/s
1.5 × 10^-35 m/s
1.5 × 10^8 m/s
2.8 × 10^8 m/s

anonymous · Answer

The equation for Force on a moving charge is:
$$F=qv \times B$$

Since it is at a right angle(90deg) with the B (magnetic) field, the cross product can go away and you're left with
$$F = qvB$$

Solve for v:
$$v = F/qB$$ 

v = (6.5x10^-14)/[(3.2x10^-19)(1.4x10^-3)]

v = 1.45x10^8 m/s which can be rounded up to 1.5x10^8 m/s

anonymous · Answer

thank you so much :)