Relative Object Speed Q: Observer Moving or Hula Hoop?

In summary, a stationary hula hoop spinning at 60rpm with an observer watching it would not be the same as spinning the outer hoop at 60rpm and remaining still. The outer hoop does not have to spin at the speed of light for it to be observed moving at the speed of light, as the speed of light limit only applies to inertial reference frames.
  • #1
PaulRacer
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If you had a stationary hula hoop in space 186,000 miles in circumference with a seat attached to the center spinning at 60rpm with an observer watching the hoop "spin" with no reference point, would this be the same as spinning the outer hoop at 60 rpm and the central observer remaining still? My point is, does the outer hoop have to actually be spinning at the speed of light for it to be observed moving at the speed of light? My explanations always stink so I can try to clarify if necessary.
 
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  • #2
PaulRacer said:
If you had a stationary hula hoop in space 186,000 miles in circumference with a seat attached to the center spinning at 60rpm with an observer watching the hoop "spin" with no reference point, would this be the same as spinning the outer hoop at 60 rpm and the central observer remaining still? My point is, does the outer hoop have to actually be spinning at the speed of light for it to be observed moving at the speed of light? My explanations always stink so I can try to clarify if necessary.
No, it would not be the same. A similar scenario is to spin around on Earth and watch the moon travel in circles with a coordinate velocity (relative to your head) greater than light speed. The speed of light limit only applies to inertial reference frames.

The hula hoop can spin at any arbitrary speed relative to an accelerated reference frame, but cannot reach the speed of light relative to an inertial reference frame.
 
  • #3


A: The relative object speed in this scenario would depend on the frame of reference. If the observer is stationary and the hula hoop is spinning at 60rpm, then the relative speed between the two would be 60 revolutions per minute. However, if the observer is also spinning with the hula hoop, then the relative speed between them would be zero.

In terms of the speed of light, the outer hoop does not have to be spinning at the speed of light for it to be observed moving at the speed of light. The speed of light is a constant and is not affected by the speed or motion of other objects. So, regardless of whether the outer hoop is spinning at the speed of light or not, the observer would still perceive the light from the hoop as moving at the speed of light.

I hope this helps clarify your question. Let me know if you have any further questions.
 

1. What is relative object speed?

Relative object speed refers to the speed at which an object is moving in relation to another object or observer. It takes into account the movement and position of both objects.

2. How does an observer's movement affect relative object speed?

An observer's movement can affect relative object speed in two ways. If the observer is moving in the same direction as the object, the relative speed will increase. If the observer is moving in the opposite direction, the relative speed will decrease.

3. What is the role of a hula hoop in relative object speed?

A hula hoop can be used as a visual representation of relative object speed. The observer can stand in the center and observe the movement of objects around them, which can help to understand the concept of relative object speed.

4. How does the distance between objects affect relative object speed?

The distance between objects does not directly affect relative object speed. However, the perceived relative speed may change if the distance between objects changes, as it can alter the perspective of the observer.

5. Can relative object speed be measured?

Yes, relative object speed can be measured by calculating the difference in speed between the two objects or by using specialized equipment such as radar guns or laser rangefinders.

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