# The Naked Scientists Forum

### Author Topic: kicking balls  (Read 4288 times)

#### paul.fr

• Guest
##### kicking balls
« on: 11/05/2007 22:14:32 »
If i kick a football, rugby ball...with x force on a hot day. will i go further than if i kicked it, with the same x force on a cold day?

Why, why not?

#### another_someone

• Guest
##### kicking balls
« Reply #1 on: 11/05/2007 23:10:41 »
I suppose it depends on whether the ball has top spin or not.

On a hot day, assuming we have still air in all cases, the density of the air will be slightly less, so the drag on the ball will be slightly less, but so would any lift that might ensue if you put top spin on the ball.

Not that I would expect the effect to be very noticeable, and I would expect the effect of the temperature on your own physiology would be greater than the effect of the temperature on the aerodynamics of flight of your ball.

#### Batroost

• Sr. Member
• Posts: 276
• There's no such thing as a dirty atom!
##### kicking balls
« Reply #2 on: 11/05/2007 23:21:09 »
Makes a difference flying aircraft though. Max take-off wieghts for small planes are air temperature and pressure dependent.

#### another_someone

• Guest
##### kicking balls
« Reply #3 on: 11/05/2007 23:32:56 »
Makes a difference flying aircraft though. Max take-off wieghts for small planes are air temperature and pressure dependent.

Yes, I would agree with this - this is because of the lower lift in hot air - which is where the topspin would come in.  The difference is that an aircrafts flight characteristics are totally governed by available lift, whereas for a football, the flight is predominantly ballistic, with only a small percentage being added by the aerodynamic.

#### lyner

• Guest
##### kicking balls
« Reply #4 on: 13/05/2007 12:22:06 »
The density of air reduces by about 3% as the air temperature increases by 10 degrees C. It would be reasonable to expect that it would produce a small but measurable effect on the drag acting against the ball.

#### The Naked Scientists Forum

##### kicking balls
« Reply #4 on: 13/05/2007 12:22:06 »