Given two vectors A and B how do we obtain the vector/cross prodcut, A x B?
(1) Geometric method
(i) Align the tails of the two vectors, by parallel-shifting one of them.
(ii) Imagine rotating A to B with the tail fixed.
(iii) The right-hand rule is then applied to figure out the direction of A x B.
(iv) The magnitude is given by ABsin(theta), where theta is the angle between A and B.
(2) Numerical mothod
A = (Ax, Ay, Az), B = (Bx, By, Bz) => A x B = (AyBz - AzBy, AzBx - AxBz, AxBy - AyBx)
These two methods are equivalent to each other, of course. In my course, you are not asked to use (2). In later courses of Phys 6, you might have a chance to do that.
Here is a simple example, in the context of the torque.

1 comment:
Does anyone else need more time for this homework? I am pretty sure I won't be able to finish by 9am tomorrow.
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