Rotational and Translational Equilibrium
Date: Fall 2013
What is necessary for an object to be in complete rotational and translational equilibrium?
In the form of energy, the statics and the dynamics in equilibrium would mean its Potential Energy (energy as a product of its mass, height, and the force due to gravity) and its Kinetic Energy (the product of 1/2 its mass and velocity -squared) are equal to zero.
Simply, its height is at ground level, and is at rest.
In short, no unbalanced forces acting on the body. Although a body can be moving and even spinning, as long as it is not speeding up either way, it is equilibrium.
For example, you can be flying on a jet airliner at 350 mph and it is as if you are siting still. You can pour liquids or get up and walk around as if you were sitting on the ground. Same thing if you are in a car going a set speed.
Hope this helps.
Translational equilibrium requires that all forces add up to a zero net force. Rotational equilibrium requires that all torques add up to a zero net torque. To have complete motional equilibrium, both net force and net torque must be zero. An object in equilibrium can be moving. It can also be rotation. However, the motion (both translational and rotational) will not change.
Dr. Ken Mellendorf
Illinois Central College
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