Rotational Inertia
Source: Nicholas Timmons, Asantha Cooray, PhD, Department of Physics & Astronomy, School of Physical Sciences, University of California, Irvine, CA
Inertia is the resistance of an object to being accelerated. In linear kinematics, this concept is directly related to the mass of an object. The more massive an object, the more force is required to accelerate that object. This is seen directly in Newton's second law, which states that force is equal to mass times acceleration.
For rotation, there is a similar concept called rotational inertia. In this case, rotational inertia is the resistance of an object to being rotationally accelerated. Rotational inertia is dependent not only upon mass, but also upon the distance of mass from the center of rotation.
The goal of this experiment is to measure the rotational inertia of two rotating masses and to determine the dependence upon mass and distance from the axis of rotation.
1. Measure the moment of inertia of the long rod.
- Wind the string attached to the weight until the weight is near the spinning arm.
- Drop the weight and measure the time it takes to drop, as well as the distance it drops.
- Perform step 1.2 three times and calculate the average moment of inertia using Equation 7.
- Compute the theoretical moment of inertia of the spinning rod using the following formula:
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| Theoretical Value
(kg m2) |
Experimental Value
(kg m2) |
Difference
(%) |
|
| Part 1 | 0.20 | 0.22 | 10 |
| Part 2 | 0.08 | 0.07 | 14 |
| Part 3 | 0.02 | 0.02< Application and Summary Have you ever wondered why a tightrope walker carries a very long pole? The reason is that the long pole has a very large moment of inertia due to its length. Therefore, it requires a large amount of torque to make it rotate. This helps the tightrope walker to stay balanced, as the pole will remain steady. Wheels of cars and bicycles are never just solid disks; instead, they have spokes that support the wheel from the axle. This allows for a lighter design, which aids with speed, Howev Tags Skip to... Videos from this collection:  Now Playing Rotational InertiaPhysics I 43.0K Views  Newton's Laws of MotionPhysics I 74.4K Views  Force and AccelerationPhysics I 77.8K Views  Vectors in Multiple DirectionsPhysics I 181.3K Views  Kinematics and Projectile MotionPhysics I 71.6K Views  Newton's Law of Universal GravitationPhysics I 188.4K Views  Conservation of MomentumPhysics I 42.7K Views  FrictionPhysics I 52.2K Views  Hooke's Law and Simple Harmonic MotionPhysics I 60.7K Views  Equilibrium and Free-body DiagramsPhysics I 37.1K Views  TorquePhysics I 23.8K Views  Angular MomentumPhysics I 35.6K Views  Energy and WorkPhysics I 49.1K Views  EnthalpyPhysics I 59.4K Views  EntropyPhysics I 17.2K Views ABOUT JoVE Copyright © 2025 MyJoVE Corporation. All rights reserved |
