Spinning Definition and 581 Threads

Ok, so the Earth spins around its axis, and around the sun; and the sun spins around the black hole at the center of the Milky Way galaxy; and that center spins around some other monster black hole at the galactic center of a cluster of galaxies, which, in turn spins about another monster...

Hi to you all, May I just say I am not a physicist or the like so my questions may seem a bit green to you all, I wish to make something and need a little bit of info please. With regards to a vacuum sphere, if I was to spin an item within it would it spin freely or would there be forces...

ok so I've got the three components of the inertia tensor (A,A,C) and I've derived expression for, using matrices, the angular velocities w1,w2,w3 (these expressions can be found online if you don't already know them). anywho, what i need to do next is use the fact that torque = rate of change...

..and he brings in his arms to decrease his moment of inertia in order to increase his angular velocity, that means the rotational kinetic energy increases. But that means there's a change in rotational kinetic energy, right? But wouldn't there be no external forces acting on him (assuming no...

Practice question for a general physics exam - I'm a 4th year undergraduate but have mostly taken astrophysics courses this year so am a bit stuck going back to general physics... Homework Statement A skater spins with angular velocity \omega = 6 rad/s with his arms extended. How fast will...

For a stationary disk, the air pressure on the platter is atmospheric pressure. For a disk spinning at 10,000 RPM, say 140 miles per hour for a 5.25 inch disk, I assume the Bernoulli effect would reduce the pressure, but because of the Ekman flow, the pressure would be more than the pressure...

Homework Statement A uniform stick 1.0 m long with a total mass of 220 g is pivoted at its center. A 3.2 g bullet is shot through the stick midway between the pivot and one end The bullet approaches at 250 m/s and leaves at 140 m/s With what angular speed is the stick spinning after the...

I was watching a video on where this guy spins a a dial or capsule or a cap (I couldn't really tell, but it was like a long thing cylinder capsule look a like) and well he gave it a quick push and the cap came to a stop and than reverses direction. What could cause this? I know that...

Before the final rocket stage the Mars lander was set spinning with an angular velocity directed along the engine force vector. I am completely lost to why they did this. By spinning the lander do they speed it up? Using the right hand rule the angular velocity vector points in the direction...

Wel, this is just crazy. I've noticed something weird about spinning tops. Most of them start loosing speed, then, just before they stop, the direction of rotation is reversed! Why?! What is the force that makes them stop for a instant and then reverse the rotation? If you have no idea...

I am slipping off my spinning disc-- Homework Statement I am taking a non calculus based physics class and have hit a wall with this one. I have a horizontal spinning disc with an Angular Acceleration of .25 rad/s^2 from rest. The disc has a radius of .05 m. A pebble is placed .025m from the...

Homework Statement Calculate the magnetic force of attraction between the northern and southern hemispheres of a spinning charged spherical shell. (ex. 5.11) Homework Equations The Attempt at a Solution I already looked at this https://www.physicsforums.com/showthread.php?t=42020. I am stuck...

In discussions, and novels, about deep space missions, we frequently read of the plan to spin the spaceship to produce artificial gravity. This intuitively makes good sense. But would it work in a ship that is very, very, very far away from any stars or other matter? That is, if the ship is...

An electron has its spin vector pointing in the positive x-direction and a magnetic field vector is turned on in the positive z-direction. Question 1. Does the spin vector turn to the positive z-direction and start to precess around the z-axis? Or does is precess around the x-axis...

A bug that has a mass mb = 4 g walks from the center to the edge of a disk that is freely turning at 21 rpm. The disk has a mass of md = 12 g. If the radius of the disk is R = 30 cm, what is the new rate of spinning in rpm? Can I have some help please?

Q # 1. the film crew CANDID CAMERA replaces person's briefcase with an identical one that contains a mounted and spinning flywheel. explain what happens when the person tries to carry the briefcase around the corner?

Homework Statement A disk with a radial line painted on it is mounted on an axle perpendicular to it and running through its center. It is initially at rest, with the line at theta 0 = -90°. The disk then undergoes constant angular acceleration. After accelerating for 3.1 s, the reference...

Homework Statement A wooden rod of negligible mass and length 85.0 is pivoted about a horizontal axis through its center. A white rat with mass 0.500 clings to one end of the stick, and a mouse with mass 0.240 clings to the other end. The system is released from rest with the rod...

[SOLVED] spinning pencil Homework Statement A pencil is set spinning in an upright position. How fast must the spin be in order that the pencil will remain in the upright position? Assume that the pencil is a uniform cylinder with length a and diameter b. Find the value of the spin in...

[SOLVED] spinning top Homework Statement Please confirm the following: 1) If a the tip of a top is perfectly sharp and everything else about the top is perfect and there is no air resistance, then you can put the top to sleep forever i.e. you can make it spin around the vertical axis...

I'm having a problem finding and equation that will give me the tensile stress acting on a spinning ring, like the rim of a flywheel, that is trying to "pull itself apart". The ring has no spokes or disc, but is just a ring spinning on its axis. I need to know how fast the ring can spin...

Okay, I know there is observational evidence for spinning black holes, so therefore I must be confused about something, and I want you to tell me what. If you have a star that is spinning, therefore it has orbital angular momentum (mass revolving around a point), then as it is collapsing in...

Homework Statement A 10g steel marble is spun so that it rolls at 150rpm around the inside of a vertically oriented steel tube. The tube is 12 cm in diameter. Assume that the rolling friction is small enough for the marble to maintain 150 rpm for several seconds. During this time, will the...

The problem reads: Find the magnetic moment of a spinning shell of charge Q, radius R, and angular velocity \vec{\omega}. My solution: I split the sphere into infinitely small loops of current (from top to bottom) and add them up. I set my origin on the center of the sphere and...

Homework Statement A 4.05 kg object is attached to a vertical rod by two strings as in Figure P6.11. The object rotates in a horizontal circle at constant speed 6.50 m/s. http://www.webassign.net/pse/p6-11.gif (a) Find the tension in the upper string. (b) Find the tension in the lower...

so here is my questions since the Earth is spinning, wouldn't centrifugal force make us lighter? if we were not spinning would we be heaver? how come i do not have gravity? what is gravity

[SOLVED] spinning liquid creating a parabolic shape take a container of liquid and spin it... a parcel at any given radius (r) experiences (in the rotating frame) a force outward = mass x angular speed^2 x r and a vertical force of mg. Thus the surface curves such that the tangent to the...

I'm looking to simulate a bouncing and spinning ball in two dimensions. I have the detection working fine but I'm having a little difficulty with the physics. I have a moving ball colliding with a stationary immovable wall. I would like to know the resultant velocities of the ball in terms...

Right hand rule for Spinning things... Hi, I'm havign a hard time figuring out how the right hand rule works for Angular momentum, Angular velocity and torques. Its so confusing because At university we get problems about rotating solid bodys like a disk on a rod, and when the question...

Suppose you have a very strong, spinning disc with a diameter of say 10 km in length. At the centre the centripetal velocity is approaching the speed of light, how would we observe the outer edge of the disc to be.

This is what i don't get for things spinning in circles. So let's say you tie a mass to the end of a string, and you start swinging the string around in a circle with a constant speed. In the absence of air resistance, then the net force on the mass would be the centripetal force provided by...

A wheel has eight spokes and a radius of 37.5 cm. It is mounted on a fixed axle and is spinning at 3.75 rev/s. You want to shoot a 17.0 cm long arrow through the wheel, parallel to this axle, without hitting any of the spokes. Assume that the arrow and the spokes are very thin and evenly spaced...

I'm working on a computer simulation, but I'm not sure how to approach this problem. I want to find the change in angular velocity on an object rotating on top of a flat plane. So far this is what I have: (* == multiplication not dot product) Ff x r = I * alpha Ff x r = I * dv/dt I...

A uniform disk of radius R and mass M is spinning with angular speed ωi. It is placed on a flat horizontal surface; the coefficient of kinetic friction between the disk and surface is μk. a) Find the frictional force on the disk. b) How long will it take for the disk to come to rest. I'm...

Problem 13.30 A thin, 60.0g disk with a diameter of 7.00 cm rotates about an axis through its center with 0.240 J of kinetic energy. What is the speed of a point on the rim? Homework Equations m=.06kg r=.035m KE=.240J The Attempt at a Solution K=(1/2)*I*(w^2) I=(1/2)*M*R^2 I'm using the...

Homework Statement The angular velocity of the spinning Earth is approximately... 0.26 rad/hr 6.28 rad/hr 0.13 rad/hr or none of the above I am new at this forum as of today! I hope that somebody could show me how I should even begin this! I have no idea! Homework Equations 1 rev/s=...

In my lab, we were spinning a mass (stopper) in a uniform circular motion attached to a string. The string went through a hollow tube and at the other of the string, a weight was hanged. We were trying to find out how frequency of the revolution were affected by mass, radius and tension force...

An object has rotational inertia I. The object, initially at rest, begins to rotate with a constant angular acceleration of magnitude alpha. What is the magnitude of the angular momentum L of the object after time t? ___ So I know that I have to find angular velocity and use the equation...

How do you find the Kinetic Energy of a person spinning on a chair with 2 equal weights on each arm? A specific problem asks what the change in KE is if he moves his originally extended arms inward. I tried doing (1/2)(I)(wf)^2 - (1/2)(I)(wi)^2 where wi is initial angular velocity and wf...

Check out this page: http://www.grc.nasa.gov/WWW/K-12/TRC/Aeronautics/Ping_Pong_Curve.html Here's the picture.

Homework Statement Link to assignment The fact that it is imperfectly conducting is supplied so that the charges in the sphere will move with the same angular velocity. The B-field induced by the moving charges will be disregarded. Homework Equations...

I did a thought experiment - suppose we have a simple clock comprising a disc rotating with constant angular velocity. We can read off time inervals by counting the revs. Another observer, passing at constant velocity will see the disc rotating at a slower rate, since moving clocks run...

Homework Statement A computer is reading data from a rotating CD-ROM. At a point that is 0.0244 m from the center of the disk, the centripetal acceleration is 283 m/s2. What is the centripetal acceleration at a point that is 0.0856 m from the center of the disc? Homework Equations Ac =...

Ages ago in my physics classes my teacher would have a large metal motor that would spin very fast, it was attached to a metal board. When he asked people to hold it it felt really strange and would pull you in apparently random directions. When it didnt spin it was very heavy but when it was...

So I have two (somewhat) related questions. 1) Why is it wheel rims (or spokes) sometimes appear to spin backward? Everytime I see this it drives me crazy. I just cannot figure out how a wheel spinning real fast in one direction appears to be spinning real slow in the other direction. 2)...

Here is a little animation of an idea I have, It's a wheel that spins continuously and is powered by magnets. Here's the link : http://www.youtube.com/watch?v=uNBVQBVOJMw" The description of the video will explain my idea. Please tell if this would work in real life.

Physics Question Applying the standard physics definition of 'spin'...If one were to take a black permanent marker and draw circles of various size in various places on the top surface of a white frisbee and throw it, would the mass inside each of those individual circles be experiencing it's...

This isn't really an aerospace problem, just basic physics. Been thinking about hardSF spaceship designs. Could someone comment on my logic and maths? The basic plan has a nuclear powerplant and a habitable section connected by a long tether. the whole contraption spins to provide cetrifugal...

Ok...I cannot remember where I had seen it...I believe it was in a science book in high school because I remember a picture being associated with it. It went something like this: Some famous physicist/scientist had a very heavy gyroscope at the end of a long metal rod. He could not lift...

When I got a stick with opposite electric charges on both ends ( a macroscopic dipole) and start slowly spinning it, I get radio waves. What happens when I keep increasing the spinning velocity, do I get the whole spectra of em waves? Does the dipole send out light at a certain spinning...