# How does friction create spin in a tennis ball

1. Apr 28, 2016

### Jainal

1. The problem statement, all variables and given/known data
So I have to do a report about tennis and about the spin. I understand how the magnus effect works and how the ball will bounce but am still unable to figure out how the actual spin is created by the contact with the racquet and the moving ball

2. Relevant equations
T=Fr

3. The attempt at a solution
I have looked online and found out it has to do with the friction between the ball and the racquet while they are in contact with each other. The friction has to do with the movement in the collision where the racquet will essentially 'slide' while in contact with the ball. I just don't understand which direction this friction would be in and if there are any other factors which effect it the spin. Also how is the spin actually created.

2. Apr 28, 2016

### Ken G

Actually, I would tend to expect the ball is rolling on the racket strings, not sliding, so that's what we would call static friction (or rolling friction, which is the same thing), rather than kinetic friction (which is "sliding" friction). The idea is, if the ball rolls across the strings due to sideways motion of the racket during contact, the need to keep the point of the ball that is touching the strings not slide is to make the ball roll, and that rolling imparts the spin. You should look up rolling friction, there are insights there.

3. Apr 28, 2016

### rcgldr

It's probably a combination of the ball initially sliding then rolling on the strings, in either case there's sufficient friction to impart spin onto the ball.