# Triple product in matlab

## Homework Statement

[/B]
The scalar triple product computes the magnitude of the moment of a force vector about a specified line. It is M = ( r×F ) ⋅n , where is the position vector from the line to the point of application of the force and is a unit vector in the direction of the line. Prompt a user to enter (Fx,Fy ,Fz ), (rx, ry,rz ), and (nx,ny ,nz ); make sure, that is a unit vector and recalculate if necessary; then compute the magnitude for the case and plot the Free Body Diagram. The graph must be formatted and labelled by coding.

## Homework Equations

[/B]= M = ( r×F ) ⋅n

## The Attempt at a Solution

[/B]
i tried dot(n,cross(r,F)) for the main code but don't know how to plot free body diagram.

Last edited:

Orodruin
Staff Emeritus
Homework Helper
Gold Member
Plot the free body diagram of what?

dot(n,cross(r,F))
This should work. You could also consider
Matlab:
det([r,F,n])
assuming that r, F, and N are column matrices.

Moderator's note: two threads were merged, since they deal with the same question.

1. Homework Statement

The scalar triple product computes the magnitude of the moment of a force vector about a specified line. It is M = ( r× F) ⋅n , where is the position vector from the line to the point of application of the force and is a unit vector in the direction of the line. MATLAB: Prompt a user to enter (Fx,Fy ,Fz ), (rx, ry, rz), and (nx,ny ,nz ); make sure, that is a unit vector and recalculate if necessary; then compute the magnitude for the case and plot the Free Body Diagram. The graph must be formatted and labelled by coding.

2. Homework Equations

M = ( r× F) ⋅n

## The Attempt at a Solution

clear;
sprinf('\nCalculating the Magnitude of M\n')
r = input ('\n Enter position vector r ');
F = input ('\n Enter Force vector F ');
While l
n = input ('\n Enter direction of the line "n" unit vector ');
N = 0;
for i = 1:1:3
N = N+n(i)^2;
end
N = round (sqrt(N),3);
if N ==1
break
end
sprintf ('\ n Error.n is not a unit vector.\n')
end

M = dot(cross(r,F),n)
M = [ M 0 0 ];

Is this correct code? And I don't know how to plot free body diagram of this code..

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