Monday, June 9, 2008

Secret Of David Beckham's Free Kick


When David Beckham takes free kick, he kicks the right hand side of the ball. The ball spins anti-clockwise and curls to the left as it travels. Given that the air will be travelling over the right hand side of the ball faster than the left, why doesn’t the ball curve to the right due to the lower pressure produced?

Because the ball is spinning on itself, the air on one side of the ball is moving past it faster than the other side. Let us assume that we are looking at the ball from above it as it flies through the air. The ball spins anticlockwise, so relative to the ball, its right hand side (RHS) is moving towards the front of the ball, while its left hand side (LHS) is moving towards the back of the ball. This actually means that the air flow on the RHS is slowed down at the surface of the ball, due to friction.


On the other hand, the air flow on the LHS is speeded up. This is the source of the force. The every same principle that allows planes to fly (Bernoulli’s Principle). When air moves slightly faster, the space between molecules is very slightly increased; this means a decrease in the pressure at that point. A decrease in pressure is equivalent to a sucking force.


Similarly, when the air is slowed down on the RHS, an increase in pressure results in a pushing force. Overall, the ball will start to swerve towards the LHS. If you kick the ball with the inside of the left foot, the ball spins clockwise, and the ball this time swerves to the RHS. If you increase the spin of the ball, the force will increase.

Wednesday, June 4, 2008

Why Don't Woodpecker Get Headache??

Woodpecker have fluid surrounding their brains. They also have very large skulls and comparatively small brains, meaning their brain tissue doesn't have much momentum (momentum=mass multiply velocity) on impact - unlike, say, a human boxer. They also have shock absorbers in the beak and skull.
Dinopium benghalense(woodpecker)

Tuesday, June 3, 2008

Can You Use A Yoyo in Zero Gravity?



Not properly. Gravity reliant tricks such as 'walking dog' would be tricky, and 'cat's cradle' would be impossible, but you could make the yoyo leave and return to your hand by flickering your wrist. What would be bizarre would be the fact that the yoyo could go up and down the string in anhy direction. It would move quite slowly, and whether it would spin is debatable. If it didn't, getting it to roll back up again would be tricky due to lack of tension in the string.

Is It True That The UK Is Tilted Towards The South East

Yes. The south east of the country is slowly sinking into the sea while the north west of Scotland is slowly rising, becauseof a process called isostatic compensation, whereby something that has been covered by a heavy weight bounces back when that weight is removed. Scotland used to be covered by ice during the last ice age.