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

[mizzy]

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?

 

[rock.freak667]

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?

 

[mizzy]

potential energy = -mgh

change in KEt + change in KEr + change in PE

is that right? but what is v in KEt?

 

[rock.freak667]

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=KE_t+KE_r

you also should know that v=rω.

 

[mizzy]

So you will have mgh=KE_t+KE_r

you also should know that v=rω.

k. mass of the spool is not given so how can we solve the KEr??

 

[novop]

The m's cancel in the equation.