Energy of translation and energy of rotation

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SUMMARY

The discussion focuses on calculating the ratio of translational kinetic energy (KEtr) to rotational kinetic energy (KEr) for a uniform disk rolling without slipping. The total kinetic energy is expressed as KEtotal = KEr + KEtr, with KEr defined as 1/2 Iω² and KEtr as 1/2 mv². By substituting the moment of inertia I for a disk (I = 1/2 mr²) and the relationship between linear velocity v and angular velocity ω (v = rω), the ratio simplifies to KEtr/KEr = 2:1. This indicates that for a uniform disk, the translational kinetic energy is twice the rotational kinetic energy.

PREREQUISITES
  • Understanding of kinetic energy equations: KEtr = 1/2 mv² and KEr = 1/2 Iω²
  • Familiarity with the moment of inertia for a disk: I = 1/2 mr²
  • Knowledge of the relationship between linear and angular velocity: v = rω
  • Basic principles of rotational motion and rolling without slipping
NEXT STEPS
  • Study the derivation of kinetic energy equations in rotational dynamics
  • Explore the concept of rolling motion and its implications in physics
  • Learn about different shapes and their moments of inertia in rotational motion
  • Investigate energy conservation principles in systems involving both translational and rotational motion
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the dynamics of rotational and translational motion, particularly in the context of rolling objects.

chloechloe
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Homework Statement


How would you go about figuring out the ratio of components (rotational and translational energy) of total kinetic energy?


Homework Equations





The Attempt at a Solution


i started with KEtotal=KEr+KEtr. KEr=1/2Iw^2; KEtr=1/2mv^2
use I for a disk-I=1/2mr^2
I put KEtr over KEr KEtr/KEr for a ratio

(1/2 mv^2)/1/2Iw^2
substitute in 1/mr^2 for I and v/r for w

(1/2 mv^2)/(1/2)(1/2mr^2)(v/r)^2

cancel m, v and r and 1/2

left with (1)/(1/2)

ratio is 2:1 KEtr:KEr ??
 
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That's right. For a uniform disk that is rolling without slipping, the translational KE is twice the rotational KE. Good!
 
YAY! Thanks for confirming. I am struggling with physics.
 

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