High School Physics : Circular Motion
Study concepts, example questions & explanations for High School Physics
All High School Physics Resources
Example Questions
Example Question #15 : Circular Motion
A potter’s wheel is rotating around a vertical axis through its center a frequency of 
We can use the conservation of angular momentum in order to solve this problem. The law of conservation of angular momentum states that the momentum before the collision must equal to the momentum after the collision. Angular momentum is calculated with the equation
Before the collision we only have the potter’s wheel rotating.
We know that the moment of inertia of the wheel can be considered as a uniform disk.
We can convert the velocity of the wheel to rad/s
We can now calculate the momentum before the collision.
Now it is time to analyze the momentum after the collision. At this point we have added a piece of clay which is now moving at the same angular velocity as the pottery.
We know that the moment of inertia of the clay can be considered as a uniform disk.
We know the angular momentum at the beginning equals the angular momentum at the end.
We can now solve for the angular velocity
Example Question #1 : Rotational Angular Momentum
Determine the moment of inertia of a 
A wheel can be looked at as a uniform disk. We can then look up the equation for the moment of inertia of a solid cylinder.The equation is
We can now solve for the moment of inertia.
Example Question #17 : Circular Motion
Two spheres have the same radius and equal mass. One sphere is solid, and the other is hollow and made of a denser material. Which one has the bigger moment of inertia about an axis through the center?
Correct Answer
Both the same
The hollow one
The solid one
The hollow one
Since both spheres have the same radius and the same mass, we need to look at the equations for the moment of inertia of a solid sphere and a hollow sphere.
A solid sphere
A hollow sphere
If both of these have the same mass and radius, the only difference is the constant that is being multiplied by
In this case the hollow sphere has a larger constant and therefore would have the larger moment of inertia.
This also conceptually makes sense since all the mass is distributed along the outside of the sphere meaning it all has a larger radius. A solid sphere has mass that is both close to the center and farther away, meaning that it would have a reduced moment of inertia.
Certified Tutor
All High School Physics Resources
