# Rate of rotational inertia help

• jmb07
In summary, the conversation discusses a problem involving a figure skater spinning at a certain rate and then reducing her rotational inertia. The question is asked about the new rate of rotation and how it relates to the inertia. The final question is about the equation for angular momentum.
jmb07
I need some help just getting moving on this problem...

A figure skater is spinning at a rate of 1.6 rev/s with her arms outstretched. She then draws her arms in toward her chest reducing her rotational inertia to 64% of its original value. What is her new rate of rotation??

I'm not sure how to relate the rate to the inertia...

angular momentum

jmb07 said:
I need some help just getting moving on this problem...

A figure skater is spinning at a rate of 1.6 rev/s with her arms outstretched. She then draws her arms in toward her chest reducing her rotational inertia to 64% of its original value. What is her new rate of rotation??

I'm not sure how to relate the rate to the inertia...
What is the equation which defines the angular momentum of a body?

## 1. What is rotational inertia and how does it relate to rate of rotation?

Rotational inertia, also known as moment of inertia, is a measure of an object's resistance to changes in its rotational motion. It is the product of an object's mass and the square of its distance from the axis of rotation. Rate of rotational inertia refers to the speed at which an object's rotational inertia changes.

## 2. How is rotational inertia calculated?

The formula for rotational inertia is I = mr^2, where I is the rotational inertia, m is the mass of the object, and r is the distance from the axis of rotation. This formula assumes that the object is a point mass, meaning that all of its mass is concentrated at a single point.

## 3. What factors affect the rate of rotational inertia?

The rate of rotational inertia is affected by several factors including the mass of the object, the shape of the object, and the distance of the object's mass from the axis of rotation. Objects with larger masses and those with their mass distributed farther from the axis of rotation have a higher rate of rotational inertia.

## 4. How does rotational inertia affect an object's motion?

Rotational inertia affects an object's motion by determining how easily it can change its rotational velocity. Objects with a higher rotational inertia will require more force to change their motion, while objects with a lower rotational inertia can change their motion more easily.

## 5. Can rotational inertia be changed?

Yes, rotational inertia can be changed by altering the mass or the distribution of mass in an object. For example, holding your arms out to the sides while spinning will increase your rotational inertia, while pulling your arms in will decrease it. Additionally, changing the shape of an object can also affect its rotational inertia.

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