The physics of snooker

Were you one of those students at school who dozed off in your physics lesson when faced with 'light inextensible strings' connected to objects on a frictionless surface?

Did you snooze through conservation of momentum and coefficient of restitution? Quite possibly, I suspect.

But then were you happy to watch sports on TV, perhaps even the snooker? If so, you were seeing a master class in applied physics...

The physics behind the baize and balls

The green baize is not a frictionless surface and the collision between the snooker balls is not a perfectly elastic collision, but therein lies the skill. Coping with an imperfect world is what sets the professionals apart.

When you strike the cue ball you impart two types of energy.  Obviously the ball moves, but it also rotates – or doesn't, depending on how it was struck. It has momentum and angular momentum. This is how you play a stun shot: striking the cue ball below the centre (with that well chalked cue tip for grip) will cause the ball to spin in reverse as it travels forward. The frictional force between the ball and the baize acts against its reverse spin, slowing down the rotation. When the cue ball strikes the object ball (if judged perfectly), the cue ball will no longer be rotating. You will then have an elastic collision of equal masses, the momentum of the cue ball being completely transferred to the object ball. In other words the cue ball stops dead and the object ball moves off with the same speed that the cue ball arrived at.

If that all sounds too much like a physics lesson, take a look at this slow motion video:

It does make me wonder if Sir Isaac Newton would have made a world class snooker player!

So whilst you are enjoying the final of the World Snooker Championship just think, you are watching a game of skill played by two expert practitioners of applied physics.

Author
Dave Gladwin
Technical Marketing Specialist

Dave is a physicist by education, an experienced software developer who now specialises in technical marketing for industrial and consumer products.