Dot product and cross product are used in many cases in physics. Here are some examples:
We use the dot product cos and in vector we use the vector product sin because of the trigonometric triangle.
To multiply two vectors in 3D, you can use the dot product or the cross product. The dot product results in a scalar quantity, while the cross product produces a new vector that is perpendicular to the original two vectors.
Normally you use sine theta with the cross product and cos theta with the vector product, so that the cross product of parallel vectors is zero while the dot product of vectors at right angles is zero.
To use the right hand rule for the cross product in vector mathematics, align your right hand fingers in the direction of the first vector, then curl them towards the second vector. Your thumb will point in the direction of the resulting cross product vector.
Because in dot product we take projection fashion and that is why we used cos and similar in cross product we used sin
The right-hand rule for the cross product is a way to determine the direction of the resulting vector. To use it, align your right hand's fingers in the direction of the first vector and then curl them towards the second vector. Your thumb will point in the direction of the resulting vector.
In mathematics, the dot product is an algebraic operation that takes two equal-length sequences of numbers (usually vectors) and returns a single number obtained by multiplying corresponding entries and adding up those products. The name is derived from the interpunct "●" that is often used to designate this operation; the alternative name scalar product emphasizes the scalar result, rather than a vector result.The principal use of this product is the inner product in a Euclidean vector space: when two vectors are expressed in an Orthonormal basis, the dot product of their coordinate vectors gives their inner product. For this geometric interpretation, scalars must be taken to be Real. The dot product can be defined in a more general field, for instance the complex number field, but many properties would be different. In three dimensional space, the dot product contrasts with the cross product, which produces a vector as result.
To find the acceleration of a particle using the vector method, you can use the equation a = r x (w x v), where "a" is the acceleration, "r" is the position vector, "w" is the angular velocity vector, and "v" is the velocity vector. The cross product (x) represents the vector cross product. By taking the cross product of the angular velocity vector with the velocity vector and then multiplying the result by the position vector, you can find the acceleration of the particle.
Dot Products in Physics denote scalar results fmo vector products, e.g Work = F.D = FDCos(FD) a scalar result from the dot product of two vectors, F Force and D Displacement.
A normal vector is a vector that is perpendicular or orthogonal to another vector. That means the angle between them is 90 degrees which also means their dot product if zero. I will denote (a,b) to mean the vector from (0,0) to (a,b) So let' look at the case of a vector in R2 first. To make it general, call the vector, V=(a,b) and to find a vector perpendicular to v, i.e a normal vector, which we call (c,d) we need ac+bd=0 So say (a,b)=(1,0), then (c,d) could equal (0,1) since their dot product is 0 Now say (a,b)=(1,1) we need c=-d so there are an infinite number of vectors that work, say (2,-2) In fact when we had (1,0) we could have pick the vector (0,100) and it is also normal So there is always an infinite number of vectors normal to any other vector. We use the term normal because the vector is perpendicular to a surface. so now we could find a vector in Rn normal to any other. There is another way to do this using the cross product. Given two vectors in a plane, their cross product is a vector normal to that plane. Which one to use? Depends on the context and sometimes both can be used!
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The sine function is used in the cross product because the magnitude of the cross product of two vectors is determined by the area of the parallelogram formed by those vectors. This area is calculated as the product of the magnitudes of the vectors and the sine of the angle between them. Specifically, the formula for the cross product (\mathbf{A} \times \mathbf{B}) includes (|\mathbf{A}||\mathbf{B}|\sin(\theta)), where (\theta) is the angle between the vectors, capturing the component of one vector that is perpendicular to the other. Thus, the sine function accounts for the directional aspect of the vectors in determining the resultant vector's magnitude and orientation.