# Engineering/Physics

posted by .

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?

and r X F = -61i +22j -59k = MA
[MA]= 87.67 ft-lbs

cosα = -61/87.67 => α=134°
cosß= 22/87.67 => ß=75.5°
cosγ= -59/87.67 => γ=132.3°

Not sure exactly where I went wrong because those angles don't make any sense.

• Engineering/Physics -

If the force acts at the origin, the lever arm r about point A is the opposite vector,
r = 4i -5j -6k

• Engineering/Physics -

Thank you so much!!!

## Similar Questions

1. ### physics

A particle has a charge of +1.5 µC and moves from point A to point B, a distance of 0.19 m. The particle experiences a constant electric force, and its motion is along the line of action of the force. The difference between the particle's …
2. ### physics

A particle has a charge of +1.5 µC and moves from point A to point B, a distance of 0.19 m. The particle experiences a constant electric force, and its motion is along the line of action of the force. The difference between the particle's …
3. ### Engineering

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?
4. ### 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 …
5. ### 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 …
6. ### physics

A force in the +y direction applied at the point x=2.3m,y=1.4m gives rise to a torque of 39n*m about the origin. Find the magnitude of the force.
7. ### physics

A force Farrowbold1 of magnitude 5.00 units acts on an object at the origin in a direction θ = 34.0° above the positive x-axis. (See the figure below.) A second force Farrowbold2 of magnitude 5.00 units acts on the object in …
8. ### Physics

A force of 20 N acts toward the west. Another force acts at the same point so that the resultant of the two forces is zero. What is the magnitude and direction of the second force?
9. ### Physics

A force F1 of magnitude 6.90 units acts on an object at the origin in a direction θ = 54.0° above the positive x-axis. (See the figure below.) A second force F2 of magnitude 5.00 units acts on the object in the direction of the …
10. ### Physics

A force F 1 of magnitude 5.90 units acts on an object at the origin in a direction θ = 28.0° above the positive x-axis. (See the figure below.) A second force F 2 of magnitude 5.00 units acts on the object in the direction of the …

More Similar Questions