- #1
Strontium90
- 24
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Hi, I was working on a problem and I am having trouble in being able to solve this problem. The difficulty is that the question only presents not enough data to find the answers that it asks for.
Here is the problem in it's entirety:
A wheel whose moment of inertia is 0.4 slug.ft^2 is rotating at 1500 rev/min. (a) what constant torque is required to increase its angular velocity to 2000 rev/min? (b) How many turns does the wheel make while it is being accelerated? (c) How much work is done on the wheel?
the answers from the book are:
(a) 2.63 lb.ft
(b) 234 turns
(c) 3.86 X 10^3 ft.lb
To answer this question, you need to find what torque is used to increase the angular velocity. As far as I can tell, you cannot do that because you do not have the time it took to increase the velocity, the displacement for the increase of the velocity or the angular acceleration.
The equations that I used are:
θ = ωt + 1/2αt^2
ω = ω + αt
ω^2 = ω^2 + 2αθ
τ = Iα
The attempts that I made to find a solution involved trying to find the displacement from the acceleration of the wheel. This course of action did not lead to the answer that the book had. My best guess was the second equation, the equation for velocity, acceleration and displacement. I tried to make a guess of the amount of displacement because time, acceleration and displacement were not available.
The only information was the moment of inertia and the initial and final angular velocities of the wheel. My goal is to find a way to get information out of a problem of this nature and have a method to do this in the future. Thank you.
Homework Statement
Here is the problem in it's entirety:
A wheel whose moment of inertia is 0.4 slug.ft^2 is rotating at 1500 rev/min. (a) what constant torque is required to increase its angular velocity to 2000 rev/min? (b) How many turns does the wheel make while it is being accelerated? (c) How much work is done on the wheel?
the answers from the book are:
(a) 2.63 lb.ft
(b) 234 turns
(c) 3.86 X 10^3 ft.lb
To answer this question, you need to find what torque is used to increase the angular velocity. As far as I can tell, you cannot do that because you do not have the time it took to increase the velocity, the displacement for the increase of the velocity or the angular acceleration.
Homework Equations
The equations that I used are:
θ = ωt + 1/2αt^2
ω = ω + αt
ω^2 = ω^2 + 2αθ
τ = Iα
The Attempt at a Solution
The attempts that I made to find a solution involved trying to find the displacement from the acceleration of the wheel. This course of action did not lead to the answer that the book had. My best guess was the second equation, the equation for velocity, acceleration and displacement. I tried to make a guess of the amount of displacement because time, acceleration and displacement were not available.
The only information was the moment of inertia and the initial and final angular velocities of the wheel. My goal is to find a way to get information out of a problem of this nature and have a method to do this in the future. Thank you.