I've been dropping squash balls at different temperatures from a constant height of 1m, and measuring the height they bounce up to. I understand that as you heat the squash balls, air molecules inside the ball (which has negligible increases in mass and volume) bounce again each other and the inside of the ball more often and harder, leading to more air pressure in the ball, and thus a higher bounce. Is there any equation that links pressure or temperature with a drop height and bounce height? I've been using Boyle's law, Charles law and the pressure law to find pressure, and there are existing formulae for volumes, of course, but how can I link pressure with bounce? I assume it will involve the coefficient of restitution somewhere, but I'm unsure. Thanks a lot! :)

I have a question about Geoff Hurst's famous goal in the final of the 1966 World Cup, and it's not whether it crossed the line.

His shot hit the goal's crossbar, deflected downwards, hit the ground and bounced out, away from the goal. I have seen similar shots since.

Why does a ball that hits the underside of the crossbar nearly always bounce away from the goal after it hits the ground? The more powerful the shot, the more likely it is to do this.

Frank Horseman, Scarborough, North Yorkshire, UK

On the far north-east coast of Australia there is a rock-covered beach known as Bouncing Rock Beach. Many of the rocks are smooth and about the size of tennis balls.It is a fascinating past-time to pick up one of these and drop it on one of the larger ones, whereupon it will bounce off in a random direction, and may keep on bouncing on other rocks, sometimes for as long as 10 or 15 seconds. If it happens to hit 'just right', it may even bounce higher than its starting point.What is happening here?

Bernard SpeightBrisbaneQueensland  Australia