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