What is the total kinetic energy of the rod?

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SUMMARY

The total kinetic energy of a uniform rod rotating about an axis is calculated using both rotational and translational kinetic energy formulas. The correct expression is derived from the equations deltaKrot = 1/2Iw^2 and deltaKtrans = 1/2mv^2, where I is the moment of inertia and w is the angular velocity. The rod's kinetic energy includes contributions from both its rotation about the center of mass and the translational motion of the center of mass. The final answer aligns with option B, confirming the necessity to express all variables in terms of angular velocity (ω).

PREREQUISITES
  • Understanding of rotational dynamics and kinetic energy concepts
  • Familiarity with the moment of inertia (I) for a uniform rod
  • Knowledge of the relationship between angular velocity (ω) and linear velocity (v)
  • Ability to manipulate and simplify equations involving kinetic energy
NEXT STEPS
  • Study the derivation of the moment of inertia for various shapes, focusing on uniform rods
  • Learn how to relate angular velocity (ω) to linear velocity (v) in rotational motion
  • Explore examples of kinetic energy calculations in systems with both rotational and translational motion
  • Investigate the implications of rotating bodies in different axes of rotation
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Physics students, educators, and anyone studying mechanics, particularly those focusing on rotational motion and energy calculations.

ccarit3007
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Homework Statement


Uniform rod rotates at axel. What is the total kinetic energy of the rod?

Homework Equations


deltaKrot = 1/2Iw^2
deltaKtrans = 1/2mv^2

The Attempt at a Solution


I believe the rod has both rotational as well as translation energy because the rod is not rotating about its center of mass. I end up getting 1/2ML^2w^2+1/2Mv^2 which is not the answer choices. (The answer is B).
 

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ccarit3007 said:
I believe the rod has both rotational as well as translation energy because the rod is not rotating about its center of mass.
You can view the rod as having both rotational KE about the center of mass and translational KE of the center of mass. Or you can view the rod as in pure rotation about the given axis. Your choice. Either way, the answer will be the same.

ccarit3007 said:
I end up getting 1/2ML^2w^2+1/2Mv^2 which is not the answer choices.
Two points: (1) How did you get that expression for the rotational KE? (2) Realize that ω and v are related. Express everything in terms of ω.
 

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