Physics Lesson 7.2.1 - Moment of Force as Analogue of Force in Translational World

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Welcome to our Physics lesson on Moment of Force as Analogue of Force in Translational World, this is the first lesson of our suite of physics lessons covering the topic of Dynamics of Rotational Motion, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.

Moment of Force as Analogue of Force in Translational World

In our Physics tutorial "Moment of Force. Conditions of Equilibrium", we explained that moment of force (otherwise known as "turning effect of force") occurs when an object or system tends to rotate around a fixed point, which we called "pivot" or "turning point". Also, we explained that in a system, there are two possible conditions of equilibrium: one for the translational (linear) motion (resultant force must be zero) and the other for rotational motion (the resultant moment of force must be zero). From here, it is easy to conclude that the analogue quantity of force in rotational motion must be the moment of force, M, which - like force in translational motion - is a quantity that determines the equilibrium of the system.

Moment of force is obtained by the cross product of distance from turning point, r and the perpendicular force to the axis of rotation, F.

Mathematically, we have

M = r × F

We have also stated that the unit of moment of force is Newton × metre, [N × m].

If the system is moving, we use the concept of torque τ instead of that of moment of force M, i.e.

τ = r × F
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Moment of force was extensively discussed in tutorial "Moment of Force. Conditions of Equilibrium" and our Physics tutorial on "Torque", so there is no need to dwell too much on this concept here.

You have reached the end of Physics lesson 7.2.1 Moment of Force as Analogue of Force in Translational World. There are 8 lessons in this physics tutorial covering Dynamics of Rotational Motion, you can access all the lessons from this tutorial below.

More Dynamics of Rotational Motion Lessons and Learning Resources

Rotation Learning Material
Tutorial IDPhysics Tutorial TitleTutorialVideo
Tutorial
Revision
Notes
Revision
Questions
7.2Dynamics of Rotational Motion
Lesson IDPhysics Lesson TitleLessonVideo
Lesson
7.2.1Moment of Force as Analogue of Force in Translational World
7.2.2Moment of Inertia
7.2.3Moment of Inertia in Different Systems of Rotational Motion
7.2.4Newton's Second Law for Rotational Motion
7.2.5Angular Momentum
7.2.6Work in Rotational Motion
7.2.7Kinetic Energy in Rotational Motion
7.2.8Power in Rotational Motion

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