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maniacp08
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A wheel free to rotate about its axis that is not frictionless is initially at rest. A constant external torque of +40 N·m is applied to the wheel for 24 s, giving the wheel an angular velocity of +610 rev/min. The external torque is then removed, and the wheel comes to rest 120 s later. (Include the sign in your answers.)
(a) Find the moment of inertia of the wheel.
kg·m2
(b) Find the frictional torque, which is assumed to be constant.
N·m
This whole topic of angular/moment of inertia and torque taking its toll on me. Please bear with me, the more I read in textbook the more confused I get.
Relevant Equations:
Inertia = sum of mi * ri^2
Inertia for continuous objects = integral of r^2 dm
I would use the equation for inertia for continuous objects correct? since the textbook used the other one when given points.
The problem doesn't give us any masses/radius -- How would I start this?
For part B:
relevant equations:
Torque = r x F
Tnet = I alpha
What should I use for the Moment of Inertia for the wheel? It doesn't state it,
some exercise from the book says consider a wheel of a bicycle to be a hoop I = MR^2
Im not sure if this is correct,
I did for translation equation
Fnet = Ma
Ext F + friction = Ma
For rotation
Tnet = I alpha
RF - Rf = 1/2 M R^2 (a/R)
= F-f = 1/2 Ma
I added the two equations
2F = 3/2 Ma
a = 4F/3M
From equation 1
F+f = Ma
f = F/3
Is this even remotely correct?
Please help, thanks so much.
(a) Find the moment of inertia of the wheel.
kg·m2
(b) Find the frictional torque, which is assumed to be constant.
N·m
This whole topic of angular/moment of inertia and torque taking its toll on me. Please bear with me, the more I read in textbook the more confused I get.
Relevant Equations:
Inertia = sum of mi * ri^2
Inertia for continuous objects = integral of r^2 dm
I would use the equation for inertia for continuous objects correct? since the textbook used the other one when given points.
The problem doesn't give us any masses/radius -- How would I start this?
For part B:
relevant equations:
Torque = r x F
Tnet = I alpha
What should I use for the Moment of Inertia for the wheel? It doesn't state it,
some exercise from the book says consider a wheel of a bicycle to be a hoop I = MR^2
Im not sure if this is correct,
I did for translation equation
Fnet = Ma
Ext F + friction = Ma
For rotation
Tnet = I alpha
RF - Rf = 1/2 M R^2 (a/R)
= F-f = 1/2 Ma
I added the two equations
2F = 3/2 Ma
a = 4F/3M
From equation 1
F+f = Ma
f = F/3
Is this even remotely correct?
Please help, thanks so much.