Rotational Inertia in two cylinders

Click For Summary
SUMMARY

The discussion focuses on calculating the kinetic energies of two uniform solid cylinders, each with a mass of 1.25 kg and an angular velocity of 235 rad/s. The first cylinder has a radius of 0.18 m, while the second has a radius of 0.73 m. The moment of inertia (I) is calculated using the formula I = mr², yielding values of 0.050625 kg·m² for the smaller cylinder. The user initially miscalculated the kinetic energy, which is given by the formula KE = 0.5 * I * ω², and sought clarification on unit conversions and the correct application of angular velocity.

PREREQUISITES
  • Understanding of rotational dynamics
  • Familiarity with the moment of inertia formula (I = mr²)
  • Knowledge of kinetic energy in rotational motion (KE = 0.5 * I * ω²)
  • Basic proficiency in unit conversions, particularly radians
NEXT STEPS
  • Study the concept of rotational inertia in detail
  • Learn about the relationship between angular velocity and linear velocity
  • Explore the effects of radius on moment of inertia and kinetic energy
  • Review unit conversion techniques for angular measurements
USEFUL FOR

Physics students, mechanical engineers, and anyone interested in understanding the principles of rotational motion and energy calculations.

TheAce3317
Messages
5
Reaction score
0
Calculate the kinetic energies of two uniform solid cylinders, each rotating about its central axis. They have the same mass, 1.25 kg, and rotate with the same angular velocity, 235 rad/s, but the first has a radius of 0.18 m and the second a radius of 0.73 m.

I got 12112188.868 for ω, and 0.050625 for I


I have been using I=mr^2, and .5*Iω^2



I plugged everything in without changing any units, and got 1906125390.62499825 for the small one, which i know to be wrong. Then I thought I remembered something my teacher said about multiplying the radians by 2pi, and then I plugged all the numbers back in and got another large number.
 
Physics news on Phys.org
nvm, ran out of time. getting help from my teacher tomorrow
 

Similar threads

How Does Adding Masses Affect the Angular Velocity of a Rotating Cylinder?
  • · Replies 12 ·
Replies
12
Views
3K
Rotational Inertia: Hoop vs Disk
  • · Replies 19 ·
Replies
19
Views
5K
Calculating Moment of Inertia for a Rotating Cylinder | Physics Tutorial
  • · Replies 2 ·
Replies
2
Views
2K
Two ropes pulling on a cylinder that is translating and rotating on a plane
  • · Replies 2 ·
Replies
2
Views
1K
What is the "r" in the moment of inertia?
  • · Replies 13 ·
Replies
13
Views
3K
Rotational inertia - globes connected by a thin rod
  • · Replies 9 ·
Replies
9
Views
2K
Rotational Inertia and Net Torque with Friction
  • · Replies 10 ·
Replies
10
Views
3K
Rotational Inertia of Solid Sphere Suspended from Ceiling
  • · Replies 1 ·
Replies
1
Views
2K
Inertia of a hollow cylinder and hollow sphere
  • · Replies 4 ·
Replies
4
Views
2K
Which Object Will Roll Farther: Solid Cylinder or Hoop on an Incline?
  • · Replies 2 ·
Replies
2
Views
2K