Can I Find a Video Explanation of the Right-Hand Method for Cross-Products?

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In summary, I was trying to understand how the right-hand method of determining the direction of the z-axis (or k, whatever) actually works and I wasn't able to find an online explanation that made sense. I think I understand how it works now thanks to the help I received from the other two users.
  • #1
M_LeComte
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I'm learning about cross-products of vectors right now. What I don't get is how the right-hand method of determining the direction of the z-axis (or k, whatever) actually works. I've looked at a couple online explanations and I'm still just as confused. Is there anywhere online that I could download a movie demonstration of this? Is there an alternative to this method even?

(In case you were wondering, I am teaching myself Advanced Physics through a textbook. And I can't ask someone who is knowledgeable about physics to show me because I don't know anyone.)
 
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  • #2
Try this:

Let's say your looking for the direction of a cross b

- hold your hand open with your thumb sticking up
- line up your fingers with a so that if you were to close your fingers, you'd be moving towards b (either you keep your hand with your thumb up or you have to turn your hand upside down)
- your thumb is pointing in the direction of the cross product
 
  • #3
The part I don't get is: "line up your fingers with a so that if you were to close your fingers, you'd be moving towards b"

Do you mean pretend to grasp b? I just don't get how curling my fingers would make my hand move towards b, or anywhere.
 
  • #4
I guess this is tough to explain without a picture. You don't move your hand; you just curl your fingers. I was thinking that your book had the whole forefinger this way middle finger that way explanation which I never liked.

Maybe this one will help:
http://www.math.montana.edu/frankw/ccp/multiworld/twothree/atv/screwrule.htm

(he writes the cross product as x^y)
If you curl your fingers so that "x turns toward the vector y in the shortest way" your thumb will be pointing in the direction of the cross product (the direction you are driving the screw).
 
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  • #5
One area of physics where the cross product is used a lot is rotational forces, such as torque and centrifugal force.

So, think of a rotating cylinder. Now picture your hand representing the forces of that cylinder.

With your hand uncurled, the tips of your fingers point raially outward, signifying centrifugal force(acceleration). And the underside of your fingers and palm (not curled) represend the instantanious velocity, which is tangent to the outside of the cylinder. And then your thumb represents the axis of rotaion, where posotive (thumb up) signifies counter-clockwise rotation, and negative (thumb down) represents clockwise rotation.

Does that help? Practical examples always helped me understand.
 
  • #6
Thank you Dude and james, I think I've got it now.
 

Related to Can I Find a Video Explanation of the Right-Hand Method for Cross-Products?

What is the Right-Hand Method?

The Right-Hand Method is a technique used in mathematics and physics to determine the direction of a vector or to find the direction of the magnetic field around a current-carrying wire.

How does the Right-Hand Method work?

The Right-Hand Method involves using the right hand to visualize the direction of the vector or magnetic field. The thumb indicates the direction of the vector or current, the first finger points in the direction of the magnetic field, and the second finger points in the direction of the force.

Why is the Right-Hand Method called "ugh"?

The term "ugh" is often used humorously to refer to the frustration or difficulty some people may experience when learning or using the Right-Hand Method. It is not an official or scientific term.

When is the Right-Hand Method used?

The Right-Hand Method is commonly used in physics and engineering to determine the direction of forces or magnetic fields in a given scenario. It is also used in mathematics to visualize and understand vector operations.

Are there any limitations to the Right-Hand Method?

While the Right-Hand Method is a useful tool, it is important to note that it only works for vectors or magnetic fields in a specific plane. For more complex scenarios, other methods may be needed.

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