Relative Object Speed Q: Observer Moving or Hula Hoop?

  • Context: Graduate 
  • Thread starter Thread starter PaulRacer
  • Start date Start date
  • Tags Tags
    Relative Speed
Click For Summary
SUMMARY

The discussion centers on the physics of relative motion, specifically regarding a hula hoop in space with a circumference of 186,000 miles and an observer at its center. It concludes that the outer hoop does not need to spin at the speed of light for it to be perceived as moving at that speed; rather, the speed of light limit applies strictly to inertial reference frames. The scenario illustrates that while the hula hoop can spin at arbitrary speeds relative to an accelerated frame, it cannot achieve light speed in relation to an inertial frame.

PREREQUISITES
  • Understanding of inertial and accelerated reference frames
  • Basic knowledge of the speed of light as a universal constant
  • Familiarity with rotational motion concepts
  • Comprehension of relative velocity in physics
NEXT STEPS
  • Research the implications of Einstein's theory of relativity on relative motion
  • Study the differences between inertial and non-inertial reference frames
  • Explore the concept of coordinate velocity and its limitations
  • Investigate the effects of acceleration on perceived motion
USEFUL FOR

Physics students, educators, and anyone interested in the principles of motion and relativity in theoretical physics.

PaulRacer
Messages
44
Reaction score
0
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.
 
Physics news on Phys.org
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.
 

Similar threads

Graduate Electrodynamics of moving bodies - §2: On the relativity of... (again)
  • · Replies 35 ·
2
Replies
35
Views
5K
High School Prove the velocity of a moving object is absolute in one IRF?
  • · Replies 22 ·
Replies
22
Views
2K
Undergrad Understanding Einstein's second postulate of special relativity
  • · Replies 57 ·
2
Replies
57
Views
8K
Undergrad How Do Rockets Traveling at High Speeds Observe Each Other's Velocity?
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad How does an observer moving at relativistic speeds perceive a pulsar?
  • · Replies 34 ·
2
Replies
34
Views
3K
Undergrad Time intervals measured by stationary and moving observers
  • · Replies 43 ·
2
Replies
43
Views
4K
High School Answer Questions on Relativity & Speed of Light | Beginner Physics
  • · Replies 8 ·
Replies
8
Views
2K
Undergrad On the Relativity of Lengths and Times
  • · Replies 14 ·
Replies
14
Views
3K
High School Can an Object Exceed the Speed of Light?
  • · Replies 12 ·
Replies
12
Views
2K
Undergrad Relativity and speed of light basics
  • · Replies 59 ·
2
Replies
59
Views
6K