Spinning ball and its trajectory

Click For Summary

Discussion Overview

The discussion revolves around the trajectory of a spinning ball, particularly in the context of table tennis and its comparison to curveballs in baseball. Participants explore the effects of spin, friction, and airflow on the ball's movement, examining both theoretical and practical implications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that a topspin ball in table tennis descends faster than a non-spinning ball, suggesting a need for clarification on the physics involved.
  • Another participant compares the situation to a curveball, emphasizing the role of friction and airflow, and referencing Bernoulli's principle regarding pressure differences.
  • Some participants argue that turbulence and friction affect the ball's trajectory, with one suggesting that the spinning motion directs air upward, causing the ball to move downward due to action-reaction principles.
  • There is a discussion about the nature of friction, with some participants questioning whether it contributes to upward or downward forces and noting that friction primarily slows down the spin.
  • Concerns are raised about the conditions under which turbulence occurs, particularly in relation to the speed and spin of a ping pong ball.

Areas of Agreement / Disagreement

Participants express varying viewpoints on the effects of friction and turbulence on the ball's trajectory, with no consensus reached on the underlying mechanics or the conditions that influence these phenomena.

Contextual Notes

Some participants highlight the complexity of the interactions between spin, friction, and airflow, indicating that assumptions about these factors may vary and that the discussion is limited by the lack of specific conditions or definitions.

pixel01
Messages
688
Reaction score
1
I play tabletennis and it is obvious that with top spin, the ball go down faster than the one without any spin. I have try to explain by bernoulli, but it seems the result is opposite: top spin ball will drift more!. Anyone can help?
 
Physics news on Phys.org
It is the same as a curveball.
Friction is important. That is why pitchers try to scruff up the ball.
The air flow is slowed down on the top side.
The faster flow on the bottom side reduces that pressure by Bernie's theorem.
 
It is the same as a curveball.
Friction is important. That is why pitchers try to scruff up the ball.
The air flow is slowed down on the top side.
The faster flow on the bottom side reduces that pressure by Bernie's theorem.
Also turbulence at the top increases the pressure there.
 
It is probably easier to use the rotational model/Newton's law. The spinning motion combined with the friction directs the air upward behind the ball. Via action-reaction (conservation law), if air goes one way (up), the ball must go the other (down).
 
Meir Achuz said:
It is the same as a curveball.
Friction is important. That is why pitchers try to scruff up the ball.
The air flow is slowed down on the top side.
The faster flow on the bottom side reduces that pressure by Bernie's theorem.
Also turbulence at the top increases the pressure there.

I agree with you that friction is important. But the force caused by friction isn't up or down is it?. Friction just slows down the spin. And turbulence, it is not so clear because sometimes the ball does not fly very fast and with not much of a spin, but the phenomenon is still observed. I don't know at which speed, the turbulence begins to occur in case of a ping pong ball
 
pixel01 said:
I agree with you that friction is important. But the force caused by friction isn't up or down is it?.
Since the ball is rotating in the direction of motion, the friction force on the top surface is much larger than on the bottom surface. But even without that effect, the friction causes the air to rotate around the ball.
 

Similar threads

Undergrad Why does my ball launcher spin the ball and not launch it (air)?
  • · Replies 5 ·
Replies
5
Views
1K
High School Why Did My Tennis Serve Bounce Unusually Low?
  • · Replies 15 ·
Replies
15
Views
2K
Undergrad Gyroscopic precession of a spin-stabilized bullet
  • · Replies 10 ·
Replies
10
Views
4K
Graduate Pool Ball Physics: Questions on Impact Spins
  • · Replies 5 ·
Replies
5
Views
4K
Graduate Can a Spinning Astronaut Use a Tethered Bowling Ball to Gain Motion in Space?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad [Questions] Modeling a Baseball Pitch Trajectory in 3D Space
  • · Replies 1 ·
Replies
1
Views
2K
Undergrad Motorized top with internal unbalanced flywheel
  • · Replies 3 ·
Replies
3
Views
644
High School The physics of flywheel launchers (like tennis ball shooters)
  • · Replies 60 ·
3
Replies
60
Views
6K
Undergrad I never fully understood gyroscopic precession - toppling gyroscopes
  • · Replies 10 ·
Replies
10
Views
1K
Undergrad How can I accurately plot the trajectory of a spinning ball on a spreadsheet?
  • · Replies 5 ·
Replies
5
Views
5K