Moment of Inertia and Frequency of Oscillation

In summary, calculating the moment of inertia given frequency of oscillation requires knowing the restoring force. This is typically used for a body hung on a pivot and displaced by a small angle, resulting in simple harmonic motion. The formula for this involves torque and moment of inertia, and can be solved using the approximation for small angles. The solution will give the angular frequency, which can then be used to find the moment of inertia.
  • #1
UKDv12
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How do you calculate the moment of inertia given frequency of oscillation?
 
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  • #2
You are going to need more than just the frequency. You will need to know the restoring force.

I think the problem you are describing is a body hung on a pivot through a point on it and the body is displaced by a small angle θ with gravity acting on the centre of mass to restore equilibrium. In the limit of small θ the body executes simple harmonic motion.

For angular displacements the equivalent of F=ma is τ = I d2θ /dt2 where τ is the torque about the pivot of gravity (mg) acting at the centre of mass and I is the moment of inertia about the pivot.

Put this together and use the approximation sin θ ≈ θ for small θ and as you would for a simple pendulum solve to find ω (= dθ/dt)

since ω (= 2 [itex]\pi[/itex] f) you have solved the problem

Hope this makes sense and helps

regards

Sam
 
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What is moment of inertia and why is it important in science?

Moment of inertia is a measure of an object's resistance to changes in its rotational motion. It is calculated based on an object's mass and how that mass is distributed around its axis of rotation. It is important in science because it helps us understand how different objects will behave when subjected to forces that cause rotational motion, such as torque.

How is moment of inertia different from mass?

Moment of inertia and mass are related but distinct properties of an object. Mass is a measure of an object's resistance to changes in linear motion, while moment of inertia is a measure of an object's resistance to changes in rotational motion. In other words, mass determines how an object will respond to forces that cause it to accelerate in a straight line, while moment of inertia determines how an object will respond to forces that cause it to rotate.

What is the relationship between moment of inertia and frequency of oscillation?

The frequency of oscillation of an object is directly proportional to its moment of inertia. This means that as the moment of inertia increases, the frequency of oscillation decreases, and vice versa. This relationship can be seen in objects such as pendulums, where a longer pendulum (with a larger moment of inertia) will have a slower frequency of oscillation compared to a shorter pendulum (with a smaller moment of inertia).

How does changing the distribution of mass affect the moment of inertia?

The moment of inertia is affected by both the mass and the distribution of that mass around the axis of rotation. Changing the distribution of mass can greatly impact the moment of inertia, even if the total mass remains the same. For example, an object with most of its mass concentrated near the axis of rotation will have a smaller moment of inertia compared to an object with the same total mass but with that mass spread out further from the axis.

What factors can affect the moment of inertia of an object?

The moment of inertia of an object can be affected by several factors, including the shape and size of the object, the distribution of mass within the object, and the axis of rotation. For example, a long, thin object will have a different moment of inertia compared to a short, thick object with the same mass. Additionally, the moment of inertia can be affected by the object's orientation and the direction of the axis of rotation.

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