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dilloncyh
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1. As shown in the figure, a gyroscope consists of a uniform disk of radius r and an axle of length R through its center and along its axis. The other end of the axle is hinged on a table but its otherwise free to rotate in any direction. The gyroscope is spinning with angular velocity w with the axle inclined to the vertical direction. Find its angular velocity of precession.
My attempt:
What I thought is that the torque due to the weight of the gyroscope equals to its rate of change of angular momentum. mgRsin(theta) = d(Iw)/dt, and I get
angular velocity = 2gR/(rw^2). Is it right?2. A point charge q is at x=3R/2 on the x-axis in front of a grounded conductor hemisphere of radius on a large conductor plate perpendicular to the x-axis and in the y-z plane. The center of the hemisphere is at (0,0,0). Find the potential energy energy of the point charge.
My attempt:
Can it be done using image charge? If so, how to set up the image charge configuration? Have no idea in how to deal with that hemisphere. If I put image charges to make the hemisphere zero potential, then the plane is not and I have to put another image charge to make the plane zero potential, but that will affect the potential of the hemisphere. So do I have to keep putting image charges (and end up with an infinite series)? Or are there other important things that I have omitted?
thanks
1. As shown in the figure, a gyroscope consists of a uniform disk of radius r and an axle of length R through its center and along its axis. The other end of the axle is hinged on a table but its otherwise free to rotate in any direction. The gyroscope is spinning with angular velocity w with the axle inclined to the vertical direction. Find its angular velocity of precession.
My attempt:
What I thought is that the torque due to the weight of the gyroscope equals to its rate of change of angular momentum. mgRsin(theta) = d(Iw)/dt, and I get
angular velocity = 2gR/(rw^2). Is it right?2. A point charge q is at x=3R/2 on the x-axis in front of a grounded conductor hemisphere of radius on a large conductor plate perpendicular to the x-axis and in the y-z plane. The center of the hemisphere is at (0,0,0). Find the potential energy energy of the point charge.
My attempt:
Can it be done using image charge? If so, how to set up the image charge configuration? Have no idea in how to deal with that hemisphere. If I put image charges to make the hemisphere zero potential, then the plane is not and I have to put another image charge to make the plane zero potential, but that will affect the potential of the hemisphere. So do I have to keep putting image charges (and end up with an infinite series)? Or are there other important things that I have omitted?
thanks
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