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

AI Thread Summary
The discussion focuses on using conservation of energy to determine the angular speed of a spool as a bucket falls. The key equations involved are the kinetic energy (KE), rotational kinetic energy (KEr), and potential energy (PE). Participants emphasize that the potential energy lost by the bucket, given by mgh, is converted into translational and rotational kinetic energy. A critical relationship is established between linear velocity and angular velocity, expressed as v = rω. The absence of the spool's mass is noted, but it is mentioned that the mass cancels out in the energy equations, allowing for a solution.
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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