Lines Planes and Vectors in 3 space

In summary, to find the equation of a plane containing a given line and a point, you need to calculate the normal vector of the plane and check if it is perpendicular to the direction vector of the line. If so, the plane contains the line. If not, the plane does not contain the line.
  • #1
gregory.weld
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If the line is parallel to the vector v = < -2,1,3>, what is the equation of the plane containing L and the point B = (-2,3,1)

A) - x + y + z = 6
B) 3x - 2y - z = 4
C) x + 6y -11z = 5
D) x + 5y - z = 12
E) 2x + 10y - 19z = 7

I know we can get the equation of the line because we have a point on the line and a vector parallel

So x = xo + at, y = yo + bt , z = zo + ct

x = -2 + -2t
y = 3 + t
z = 1 + 3t

I know the equation of a plane is a(x - xo) + b(y - yo) + c(z - zo) = 0. But the vector here <a,b,c> has to be normal to the plane...
Can someone help figure out how i find the answer
 
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  • #2
gregory.weld said:
If the line is parallel to the vector v = < -2,1,3>, what is the equation of the plane containing L and the point B = (-2,3,1)

A) - x + y + z = 6
B) 3x - 2y - z = 4
C) x + 6y -11z = 5
D) x + 5y - z = 12
E) 2x + 10y - 19z = 7

I know we can get the equation of the line because we have a point on the line and a vector parallel

So x = xo + at, y = yo + bt , z = zo + ct

x = -2 + -2t
y = 3 + t
z = 1 + 3t

I know the equation of a plane is a(x - xo) + b(y - yo) + c(z - zo) = 0. But the vector here <a,b,c> has to be normal to the plane...
Can someone help figure out how i find the answer
This is a tricky question. If all you know is a point on a plane and a vector that is parallel to a line that lies in the plane, there is not enough information to specify a unique plane.

However, since they give you the equations of 5 planes, then what you need to do is pick the one (if any) that works.

For each of the 4 planes that contains the given point (one plane doesn't), calculate the normal vector, and dot it with the direction vector of the line. If the result is 0, this means that the direction vector is perpendicular to the normal vector, so must lie in the plane. If the dot product isn't zero, the given line can't lie in the plane.

That's what I would do. I haven't worked it all the way through, so I can't say whether any of the given planes works.
 

FAQ: Lines Planes and Vectors in 3 space

What is the difference between a line and a plane in 3D space?

A line is a one-dimensional object that extends infinitely in two directions, while a plane is a two-dimensional object that extends infinitely in all directions. In 3D space, a line can be represented by a direction vector and a point on the line, while a plane can be represented by a normal vector and a point on the plane.

How do you find the equation of a line or plane in 3D space?

To find the equation of a line, you need to know a point on the line and a direction vector. The equation is typically written as r = r0 + tv, where r represents any point on the line, r0 is the given point, and v is the direction vector. To find the equation of a plane, you need to know a point on the plane and a normal vector. The equation is typically written as n · (r - r0) = 0, where n is the normal vector and r0 is the given point.

What is the dot product of two vectors and how is it used in 3D space?

The dot product is a mathematical operation that takes two vectors and returns a scalar value. In 3D space, the dot product is used to find the angle between two vectors, determine if two vectors are perpendicular, and project one vector onto another. It is also used in the equation of a plane, as shown in the previous answer.

How are vectors represented in 3D space?

In 3D space, vectors can be represented in multiple ways. They can be represented as arrows, with the length representing the magnitude and the direction representing the direction of the vector. They can also be represented algebraically as ordered sets of numbers, or geometrically as points in space. In addition, vectors can be represented using components, where each component represents the magnitude of the vector in a specific direction.

What is the cross product of two vectors and how is it used in 3D space?

The cross product is a mathematical operation that takes two vectors and returns a vector that is perpendicular to both of the original vectors. In 3D space, the cross product is used to find the direction of a vector that is perpendicular to a plane, calculate the area of a parallelogram formed by two vectors, and find the moment of a force in mechanics. It is also used in the equation of a plane, as shown in the previous answers.

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