Angular and linear velocity question

In summary, when a long piece of wood is spun in a circle and then let go, the object's center of mass will continue in a straight line while the various pieces rotate about it. This is due to the object being a rigid body with a common angular velocity about the center of mass. This can be observed in hammer throw competitions, where the hammer moves in a straight line while the handle and head rotate around it. This is different from smaller objects, like balls, which will also move in a straight line due to centripetal force but have a different distribution of velocities.
  • #1
Physics is awesome
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I have a question, let’s say I’m holding a long piece of wood such as. 1’ x 6’ plank and I’m rotating it in a circle by spinning around with my hands extended, I suddenly let go, what happens to the velocity of the wood since every point on the wood that is a different distance from the center of rotation is traveling at a different linear speed. I’m assuming the wood will try to spin around it’s center of mass but how would that work when the wood is let go of has all different velocities . Was just curious because when reading about physics of centripetal force it says the object will move about in a straight line but I’m assuming that’s for small objects likes balls and such, nothing is ever discussed when you have an object that is long and is spinning and let go of. Maybe I should try spinning a board but since I don’t have a safe place to do this I figured I would ask.
 
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  • #2
The object's center of mass will continue in a straight line. The various pieces start with various velocities relative to the center of mass that amount to a rotation about that center.
 
  • #3
The wood is a rigid body. Although pieces on it have different linear velocities, they have a common angular velocity about the center of mass at all times. When you let go, these pieces will rotate about the CM while the CM will describe projectile motion in general or will move in a straight line if gravity is not acting on it.
Physics is awesome said:
Was just curious because when reading about physics of centripetal force it says the object will move about in a straight line but I’m assuming that’s for small objects likes balls and such, ...
You are assuming correctly.
 
  • #4
Check out videos from hammer throw competitions. They're doing the experiment for you.
 
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Related to Angular and linear velocity question

1. What is the difference between angular velocity and linear velocity?

Angular velocity is a measure of how fast an object is rotating around a fixed point, while linear velocity is a measure of how fast an object is moving in a straight line. Angular velocity is expressed in radians per second, while linear velocity is expressed in meters per second.

2. How are angular velocity and linear velocity related?

Angular velocity and linear velocity are related by the radius of the rotation. The linear velocity can be calculated by multiplying the angular velocity by the radius of the rotation. This relationship is described by the formula v = ωr, where v is linear velocity, ω is angular velocity, and r is the radius of rotation.

3. How does angular velocity affect linear velocity?

Angular velocity affects linear velocity in two ways. First, an increase in angular velocity will result in an increase in linear velocity, assuming the radius of rotation remains constant. Second, an object with a larger radius of rotation will have a higher linear velocity than an object with a smaller radius of rotation, even if both objects have the same angular velocity.

4. Can angular velocity and linear velocity be negative?

Yes, both angular velocity and linear velocity can be negative. A negative angular velocity indicates that an object is rotating in the opposite direction of its positive angular velocity. A negative linear velocity indicates that an object is moving in the opposite direction of its positive linear velocity.

5. How is angular velocity measured?

Angular velocity is measured in units of radians per second (rad/s). This can be calculated by dividing the angle traveled by the time it took to travel that angle. For example, if an object travels 1 radian in 0.5 seconds, its angular velocity would be 2 rad/s.

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