Angular Momentum and Conservation of Angular Motion

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SUMMARY

The discussion focuses on calculating the torque required to change the spinning rate of a 3.50 kg sphere with a radius of 7.50 m from 900 rpm to 200 rpm in 3.0 seconds. The relevant equations include torque (t = I * α), moment of inertia (I = (2/5)mr²), and the relationship between torque and force (t = F * r). The solution involves converting rpm to radians per second, calculating angular acceleration, and applying the torque formula to find the required torque of -1.92 x 10³ Nm.

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Aarron Anderson
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OP has been reminded that they need to show their work when posting schoolwork questions

Homework Statement


How much torque is needed to change the speed of spinning rate of a 3.50 kg sphere with a radius of 7.50 m from 900. rpm to 200. rpm in 3.0 s? [-1924  -1.92 x 103 Nm]

Homework Equations


t = I * α
I = (2/5)mr^2
t = F * r

The Attempt at a Solution


just can't get a crack at it.[/B]
 

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Aarron Anderson said:

Homework Statement


How much torque is needed to change the speed of spinning rate of a 3.50 kg sphere with a radius of 7.50 m from 900. rpm to 200. rpm in 3.0 s? [-1924  -1.92 x 103 Nm]

Homework Equations


t = I * α
I = (2/5)mr^2
t = F * r

The Attempt at a Solution


just can't get a crack at it.[/B]
Actually, it's very easy.
You really just have to calculate the moment of inertia and, after that, determine the angular acceleration needed to slow the spinning rate from 900 to 200 rpm. First, convert rpm to rads/s. Angular acceleration equals change in angular velocity divided by change in time. As you said, torque equals moment of inertia times angular acceleration. You will find << Answer deleted by Moderator >>
 
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