# Engineering

posted by .

A force of 26 lb. acts through a point (4; 5; -7) ft. and is equally inclined
to the positive ends of the orthogonal axes. What is the moment of this
force about the origin

So i'm assuming vector r is 4i+5j-7k?

And using the fact that cos^2α + cos^2β + cos^2γ = 1
therefore l=m=n=√1/3
I understand the force vector is equivalent to (26l + 26m + 26n) which equates to: (26/√3 i + 26/√3 j + 26/√3 k)

Thus the moment of force about the origin is (4i+5j+7k) X (26/√3 i + 26/√3 j + 26/√3 k)

This just seems very wrong to me as the cross products would yield very ugly numbers.

I have close to zero confidence in my answer

## Similar Questions

1. ### Physics

A coin slides over a frictionless plane and across an xy coordinate system from the origin to a point with xy coordinates (3.0 m, 4.4 m) while a constant force acts on it. The force has magnitude 2.3 N and is directed at a counterclockwise …
2. ### Physics

A coin slides over a frictionless plane and across an xy coordinate system from the origin to a point with xy coordinates (3.0 m, 4.1 m) while a constant force acts on it. The force has magnitude 2.4 N and is directed at a counterclockwise …
3. ### Physics

A coin slides over a frictionless plane and across an xy coordinate system from the origin to a point with xy coordinates (3.0 m, 4.1 m) while a constant force acts on it. The force has magnitude 2.4 N and is directed at a counterclockwise …
4. ### Physics

A coin slides over a frictionless plane and across an xy coordinate system from the origin to a point with xy coordinates (3.0 m, 4.1 m) while a constant force acts on it. The force has magnitude 2.4 N and is directed at a counterclockwise …
5. ### Engineering/Physics

A force F = 7^i + 6^j - 5^k lb. acts at the origin. Find the magnitude and direction cosines of the moment of this force about point A (-4; 5; 6) ft So in this case wouldn't vector r= -4i +5j +6k and vector F = 7i + 6j - 5k lb?
6. ### Physics

A force 1 of magnitude 7.20 units acts on an object at the origin in a direction θ = 29.0° above the positive x-axis. (See the figure below.) A second force 2 of magnitude 5.00 units acts on the object in the direction of the …
7. ### physics

A force 1 of magnitude 5.40 units acts at the origin in a direction 45.0° above the positive x axis. A second force 2 of magnitude 5.00 units acts at the origin in the direction of the positive y axis. Graphically find the magnitude …
8. ### Physics

A 49-N force is applied perpendicular to the portion BC of the bent bar. Determine the moment of P about point B and about point A. The image shows a bar that is straight from point A to B but then bends at a 42 degree angle to the …
9. ### ph

A coin slides over a frictionless plane and across an xy coordinate system from the origin to a point with xy coordinates (3.0 m, 5.8 m) while a constant force acts on it. The force has magnitude 2.8 N and is directed at a counterclockwise …
10. ### Physics

A small mass slides without friction across a plane an (x,y) coordinate system directly from the origin to a point with (x,y) coordinates (1.3 m, 9.6 m); a constant force acts on it. The force has magnitude 2.1 N and its direction …

More Similar Questions