- #1

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Express your answer in terms of m, r , n ,t and, pi .

does anyone have any pointers for me?

i do know that this formula, 1/2mr^2 can help me, but i dont know how create the right equation using the other arts given to me.

- Thread starter badman
- Start date

- #1

- 57

- 0

Express your answer in terms of m, r , n ,t and, pi .

does anyone have any pointers for me?

i do know that this formula, 1/2mr^2 can help me, but i dont know how create the right equation using the other arts given to me.

- #2

- 551

- 1

Rotational kinetic energy is given by

[tex]KE_{rot} = \frac{1}{2}I\omega^2[/tex].

Just write everything in terms of the variables you've been given.

[tex]KE_{rot} = \frac{1}{2}I\omega^2[/tex].

Just write everything in terms of the variables you've been given.

Last edited:

- #3

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1/2*m*r^2*((2*PI)/n*t)^2. can anyone point me in the right direction

- #4

- 551

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In your angular velocity, your n should be in the numerator of the fraction.

- #5

BobG

Science Advisor

Homework Helper

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Two problems with your answer.badman said:

1/2*m*r^2*((2*PI)/n*t)^2. can anyone point me in the right direction

You're using moment of inertia for a ring, not a solid wheel of uniform density. Technically, moment of inertia is:

[tex]I = \int_0^m r^2 dm[/tex]

Unless you have to solve the integrals, it's usually easier to look up the solution. Moment of inertia of several shapes are at Eric Weisstein's World of Physics (you need to scroll down a little to see the formulas)

Your angular velocity is measured in radians per second. You were given

[tex]\frac{n_- revs}{t_- sec} * \frac{2 \pi_- rad}{1_- rev} = \omega[/tex]

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