Calculating Angular Speed in a Rotating System with Sliding Rings

In summary, a uniform rod with two sliding rings is rotating in a horizontal plane at an angular velocity of 35.0 rev/min. When the rings reach the ends of the rod, the angular speed of the system is 2.27 rpm. This is also the same angular speed of the rod after the rings leave it.
  • #1
lina29
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A uniform rod of mass 2.95×10−2 kg and length 0.440 m rotates in a horizontal plane about a fixed axis through its center and perpendicular to the rod. Two small rings, each with mass 0.240 kg, are mounted so that they can slide along the rod. They are initially held by catches at positions a distance 4.70×10−2 m on each side from the center of the rod, and the system is rotating at an angular velocity 35.0 rev/min. Without otherwise changing the system, the catches are released, and the rings slide outward along the rod and fly off at the ends.

A-What is the angular speed of the system at the instant when the rings reach the ends of the rod?

B-What is the angular speed of the rod after the rings leave it?

Using these equations I get
I1 = (1/12)(m1)L² + 2(m2)r²=.00154
I2 = (1/12)(m1)L² + 2(m2)(L/2)²=.02371
ω2 = ω1(I1/I2)
I know the answer for a and b are the same I'm just confused how I use ω2 = ω1(I1/I2) to figure out the answer
 
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  • #2
lina29 said:
I know the answer for a and b are the same I'm just confused how I use ω2 = ω1(I1/I2) to figure out the answer

Are you sure the answers are the same?
 
  • #3
Yes. I figured it out though. I realized that I was given w1 and w2 = 35*[.00154/.02371] = 2.27 rpm.

Thanks though!
 

1. What is angular speed in physics?

Angular speed is a measure of how fast an object is rotating around a central axis. It is typically measured in radians per second (rad/s) or degrees per second (deg/s).

2. How is angular speed different from linear speed?

While linear speed measures the rate of change of position in a straight line, angular speed measures the rate of change of angular displacement. In other words, linear speed is the distance an object travels in a certain amount of time, while angular speed is the angle an object rotates through in a certain amount of time.

3. What is the formula for calculating angular speed?

The formula for angular speed is angular speed (ω) = angular displacement (θ) / time interval (t). It can also be written as ω = 2πf, where f is the frequency of rotation in hertz (Hz).

4. How does angular speed relate to linear speed?

Angular speed and linear speed are related through the radius of rotation (r). The linear speed of an object at a certain angular speed can be calculated by multiplying the angular speed by the radius of rotation: v = ωr. This relationship is known as tangential velocity.

5. Can angular speed be negative?

Yes, angular speed can be negative if an object is rotating in the opposite direction of the chosen positive direction. This is known as negative angular speed, and it is still measured in the same units (rad/s or deg/s) as positive angular speed.

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