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Physics Dad
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Question
The Hubble Space Telescope is stabilized to within an angle of about 2 millionths of a degree by means of a series of gyroscopes that spin at 1.92×104 rpm . Although the structure of these gyroscopes is actually quite complex, we can model each of the gyroscopes as a thin-walled cylinder of mass 2.00 kg and diameter 5.00 cm , spinning about its central axis.
How large a torque would it take to cause these gyroscopes to precess through an angle of 1.20×10-6 degree during a 5.00 hour exposure of a galaxy?
Equations
I=mr2
L=Iω
Ω=dΦ/dt
τ=ΩL
Variables and Conversions
m=2.00kg
r=0.025m
dΦ=(1.20×10-6×2π)/360 = 2.09×10-8 rad
dt=5×60×60=1800s
ω=(1.92×104×2π)/60 = 640π rad/s
Attempt at Solution
I=(2.00kg)(0.025)2=1.25×10-3kgm2
L=(1.25×10-3kgm2)(640π)=4π/5
Ω=(2.09×10-8)/(1800)=1.16×10-12
τ=(1.16×10-12)(4π/5)
=2.92×10-12Nm
My answer is incorrect. Any help would be greatly appreciated. This is the ridiculous "mastering physics" website. It is the most pointless thing ever. I would much rather we were given an assignment to complete as at least then you can receive constructive feedback as opposed to simply being told the answer is wrong.
I am happy to be wrong as long as I can understand why. I am sure I have just made a simple mistake, like use the wrong equation or miscalculate something, but with no guidance I can't fix it.
Thank you.
The Hubble Space Telescope is stabilized to within an angle of about 2 millionths of a degree by means of a series of gyroscopes that spin at 1.92×104 rpm . Although the structure of these gyroscopes is actually quite complex, we can model each of the gyroscopes as a thin-walled cylinder of mass 2.00 kg and diameter 5.00 cm , spinning about its central axis.
How large a torque would it take to cause these gyroscopes to precess through an angle of 1.20×10-6 degree during a 5.00 hour exposure of a galaxy?
Equations
I=mr2
L=Iω
Ω=dΦ/dt
τ=ΩL
Variables and Conversions
m=2.00kg
r=0.025m
dΦ=(1.20×10-6×2π)/360 = 2.09×10-8 rad
dt=5×60×60=1800s
ω=(1.92×104×2π)/60 = 640π rad/s
Attempt at Solution
I=(2.00kg)(0.025)2=1.25×10-3kgm2
L=(1.25×10-3kgm2)(640π)=4π/5
Ω=(2.09×10-8)/(1800)=1.16×10-12
τ=(1.16×10-12)(4π/5)
=2.92×10-12Nm
My answer is incorrect. Any help would be greatly appreciated. This is the ridiculous "mastering physics" website. It is the most pointless thing ever. I would much rather we were given an assignment to complete as at least then you can receive constructive feedback as opposed to simply being told the answer is wrong.
I am happy to be wrong as long as I can understand why. I am sure I have just made a simple mistake, like use the wrong equation or miscalculate something, but with no guidance I can't fix it.
Thank you.