- #1
bmxicle
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Homework Statement
a particle with charge -2.00 C initially moves at v = 1.00 i^hat + 7.00 j^hat. If it encounters a magnetic field B = 60.00 k^hat T, find the force on the particle
Homework Equations
F = Q (v x B)
The Attempt at a Solution
I set up a matrix to find the cross product.
v x B = det i j k
1 7 0
0 0 60
If you expand along row three you get (-1)^(3+3) * (60) det i j
1 7
= 60(7i-1j)
===> F=(-2.0 C)(60)(7i - 1j) = -840i + 120 j
The answer i was given has the signs reversed, and i can't figure out why. I've tried it drawing diagrams too and i still got the same answer.