Use conservation of energy to determine the angular speed of a spool

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SUMMARY

The discussion focuses on using the conservation of energy principle to determine the angular speed of a spool when a 3.0 kg bucket falls 4.00 m. The key equations involved are the kinetic energy equations for translational (KEt = 1/2 mv^2) and rotational (KEr = 1/2 I ω^2) motion, along with potential energy (PE = mgh). The relationship established is mgh = KEt + KEr, where the translational velocity v is related to angular velocity ω by the equation v = rω. The mass of the spool is not provided, but it is noted that the mass cancels out in the energy equations.

PREREQUISITES
  • Understanding of conservation of energy principles
  • Familiarity with kinetic energy equations (translational and rotational)
  • Knowledge of the relationship between linear and angular motion (v = rω)
  • Basic algebra for manipulating equations
NEXT STEPS
  • Study the derivation of the conservation of energy principle in mechanical systems
  • Learn about the moment of inertia (I) for different shapes, particularly for spools
  • Explore examples of energy conservation problems involving pulleys and spools
  • Practice solving problems that involve both translational and rotational kinetic energy
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators looking for examples of energy conservation in rotational systems.

mizzy
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Homework Statement



Use conservation of energy to determine the angular speed of a spool after the bucket(3.0kg) has fallen 4.00m, starting from rest.

Homework Equations


KE = 1/2mv^2

KEr = 1/2 * I * omega^2

PE - mgh


The Attempt at a Solution



i don't know how to start. I know that I'm suppose to add the change in kinetic translational and kinetic rotational and potential energies.

Can someone guide me on this please?
 
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As the bucket falls 4m, what is the energy associated here and what is its quantity?

This energy is converted into translational and rotational kinetic energy, so can you form an equation relating the three equations?
 
potential energy = -mgh

change in KEt + change in KEr + change in PE

is that right? but what is v in KEt?
 
mizzy said:
potential energy = -mgh

change in KEt + change in KEr + change in PE

is that right? but what is v in KEt?

So you will have mgh=KEt+KEr

you also should know that v=rω.
 
rock.freak667 said:
So you will have mgh=KEt+KEr

you also should know that v=rω.

k. mass of the spool is not given so how can we solve the KEr??
 
The m's cancel in the equation.
 

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