Intermediate Axis Theorem.... fun to learn it again with You Tube

AI Thread Summary
The discussion revolves around the intermediate axis theorem, illustrated through a YouTube video featuring a rotating wingnut in a space station. The theorem, learned during undergraduate physics, is applied to practical experiences like knife throwing and ping pong paddle flipping. The mechanics of knife throwing are detailed, emphasizing the importance of the knife's longest rotational axis aligned with its flight direction, and how the rotation is affected by the thrower's technique. A typical knife throw covers about 9 meters with a specific rotation pattern, highlighting the connection between physics principles and real-world applications. The conversation also touches on the similarities between knife and axe throwing, particularly regarding stability in flight and the follow-through motion.
CPW
Messages
51
Reaction score
30
A friend of mine shared a YouTube video with me, saying he was sure I would love it. He described it as very strange with a rotating wingnut in the space station flipping over on its rotation axis, over and over, while it spun rapidly.

After watching the video, I verified I was taught the intermediate axis theorem in my undergraduate physics mechanics class.

Grabbing my ping pong paddle from my basement, I have been entertained by attempting to flip the racquet about the intermediate axis and had fun showing my family. You might too enjoy this topic.
 
Reply
  • Like
Likes Lnewqban, Klystron and BillTre
Physics news on Phys.org
I learned a bit about these theorems while practicing knife throwing. You throw a knife nearly the same as throwing a baseball or cricket ball; use your hand, arm and wrist to power the flight and your fingers to spin the ball or blade. Balls have spherical symmetry but knives have three distinct rotational axes.

The knife thrower cares primarily about rotation of the longest axis of the knife vertically aligned with direction of flight, rotating at an origin roughly 3cm along the blade measured from the interior end of the haft (handle) for a 20cm knife. This rotation origin corresponds to the knife's center of gravity (cog). The amount of rotation imparted to the knife, measured in 1/2 turns, depends on the distance to the target. When the knife is grasped by the blade, one half turn represents the shortest flight distance to strike point first.

A typical throw covers a distance of 9m (10 yards) in 1.5 turns, ending point first in the target. The throw begins in the hips, travels down the throwing leg and arm, continues with the 'flip' or rotation imparted by the fingers at release as the arm points toward the target, and finishes with a distinct follow through motion of the hand, arm and entire body much like a pitcher.
 
Last edited:
Here's an application of the theorem from the Le Mans automotive racetrack.

 
Reply
  • Wow
  • Like
Likes CPW and BillTre
I guess this idea deserves a vid. This clip from wiki shows an overhand axe throw but the same principles apply.
310px-slow_motion_axe_throwing-gif.gif


Axe throwing in slow motion

Notice the rotation along the longest axis for stability in flight and the exaggerated follow through of the entire body
 

Hot Threads

Recent Insights

Back
Top