Why is AXB not equal to BXA?

In summary, the problem is to show that the equation AXB is not equal to BXA. The solution involves finding a counterexample, as the problem is not asking for a proof that AxB and BxA are unequal for every possible A and B. By trying examples, it can be seen that the two equations are not equal.
  • #1
jcsolis
38
1

Homework Statement




Show that AXB is not equal to BXA

No variables given..just this equation


Homework Equations






The Attempt at a Solution



I don´t know how to start...the only thing I know so far is that AXB is equal to -BXA
 
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  • #2
Have you tried any examples at all? After all, if you know that AxB = -BxA, shouldn't it be very easy to find a counterexample?
 
  • #3
let me try
 
  • #4
A little comment on semantics... when a question asks you to prove an identity is invalid; e.g. to show that AxB is not BxA, that means you just need to find one counterexample. In particular, the problem is not asking you to prove AxB and BxA are unequal for every possible A and B.
 
  • #5
Thanks for the help...I didn´t understand why it´s not equal and now I get it
 

1. What is the cross product in statics?

The cross product, also known as the vector product, is an operation that takes two vectors and produces a third vector that is perpendicular to both of the original vectors. In statics, the cross product is used to find the moment of a force about a point, which is important in analyzing the equilibrium of a rigid body.

2. How do you calculate the cross product in statics?

The cross product of two vectors, A and B, is calculated by taking the magnitude of A, the magnitude of B, and the sine of the angle between them, and then multiplying them together. The result is a vector that is perpendicular to both A and B, and its direction is determined by the right-hand rule.

3. What is the difference between the cross product and the dot product in statics?

The cross product and the dot product are both mathematical operations involving vectors, but they have different results. The dot product produces a scalar (a number), while the cross product produces a vector. In statics, the dot product is used to calculate the work done by a force, while the cross product is used to calculate the moment of a force.

4. How is the cross product used in solving statics problems?

In statics, the cross product is used to calculate the moment of a force about a point. This is important in determining the equilibrium of a rigid body, as the sum of all moments must be equal to zero for the body to be in static equilibrium. The cross product is also used in calculating the torque exerted by a force on a rigid body.

5. Can you use the cross product to solve 2D statics problems?

Yes, the cross product can be used in 2D statics problems, but it is typically only necessary in cases where the forces are not coplanar (lying in the same plane). If all of the forces in a 2D problem are coplanar, the cross product will result in a vector pointing directly out of the plane, which can be ignored in 2D calculations. However, in 3D statics problems, the cross product is essential for finding the moment of a force about a point.

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