Why Are the Moments Negative on Fb, Fc, and Fd?

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SUMMARY

The discussion clarifies why the moments on forces Fb, Fc, and Fd are negative, emphasizing the relationship between torque and rotational direction. The torque of a force F at point r is calculated using the vector product of r and F, resulting in the equations Mx=y Fz -z Fy, My=z Fx -x Fz, and Mz=x Fy -y Fx. The sign of the moment is determined by the direction of rotation: moments are positive for anti-clockwise rotation and negative for clockwise rotation.

PREREQUISITES
  • Understanding of vector products in physics
  • Familiarity with torque and its calculation
  • Knowledge of rotational dynamics
  • Basic grasp of Cartesian coordinate systems
NEXT STEPS
  • Study the principles of torque in physics
  • Learn about vector cross products and their applications
  • Explore the concept of rotational equilibrium
  • Investigate the effects of different forces on moments in 3D space
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Students of physics, engineers, and anyone studying mechanics or rotational dynamics will benefit from this discussion.

noname1
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This is not really a homework question just a review but i wanted someone to explain to me why the forces of the moments negative on Fb, Fc and Fd

thanks in advanced
 

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The component of torque of a force F acting at a point r is equal to the vector product of the vector r and the force.
Mx=y Fz -z Fy,
My=z Fx -x Fz,
Mz=x Fy -y Fx.

You can also decide the sign from the direction of rotation the force would cause along an axis. Seeing from the positive x, y, or z axis, the moment is positive if it rotates anti-clockwise, and negative, if the rotation is clockwise.

ehild
 

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