Alright class, I am behind on the syllabus as usual. That said, lets get right into today’s lecture.

We’ve all heard of soccer stars like David Beckham bending a soccer ball to curve it around the goalkeeper or aim corner kicks. But before understanding how bending occurs we need to know what bending is.

Simply put, bending is when a soccer ball travels in a path that is curved compared to a ball that was kicked from the same location which travels in a straight line. Think of it like a curve ball.

The basics of a curve ball begin with the ball itself. If a baseball is scuffed or dirty it will act differently than a smooth, clean ball. The same holds true in soccer.

“There are some soccer balls that are more lively than others,” NIU men’s soccer coach Steve Simmons said. “If you’re using a lower-class ball it’s harder to bend.”

Factors such as the stitching on the ball, how heavy the inner bladder is, the number of seams and more determine this liveliness…or lack of. For our sake, let’s ignore these factors and say we have a lively ball. The shape of the player’s foot is key. This shape will dictate the rotation and velocity of the ball. Before we go any further in explaining this, we need to understand what velocity and rotation are.

The velocity is the speed and path of the ball. And the rotation of the ball is simply the amount of spinning that is occurring.

Now, for a player to bend the ball there must be a balance between the energy that is put into the forward motion of the ball and the amount the ball rotates. This is greatly determined by the shape of the player’s foot.

“You have to wrap your foot around the ball, as you’ll be able to get the curling motion that will produce the spin,” Simmions said. “But, if you spin the ball too much you’ll get the energy all in the spin and not in the velocity of the ball.”

But why all the focus on the spin?

As the ball rotates it forces air to go around it at different speeds. This is due to the fact that the edges of the ball are moving at different velocities.

While all the edges of the ball are moving at the same speed, they are moving in different directions. This creates different pressures to be applied to the ball.

“The point is the pressure of the air goes down on the side of the ball, when the velocity of the air increases due to Bernoulli’s effect,” NIU associate physics professor Larry Lurio said. “When one side of the ball speeds up the air, the other side of the ball slows down the air. The side where the air goes faster is the side with lower pressure, where as the side with the air moving slower around the ball has a higher pressure.”

Newton’s third law of motion states that for every action there is an equal and opposite reaction. The low pressure forces large amounts of air to flow in one direction from the ball. But the high pressure does not create an equal amount of air following in the opposite direction.

Thus, for the reaction to be equal and opposite, the ball has a force pushing it in the opposite way of the high pressure. This causes our soccer ball to bend.

Well I seem to be out of time. Don’t forget, we will be examining the back spin of a golf ball next time and will have a short quiz afterwards.

Ben Gross is a NIU football beat reporter for the Northern Star and a physics major.