This is mt presentation script about knuckle ball.

Check my grammar and make it clear. And I don't know how to conclude... help me about conclude part too.

The physics behind many sports, including soccer, helps us to better understand the science involved in the sport and can also help us perhaps play the sport more efficiently. Today, I would like to present about knuckle kick in soccer. One of the key aspects of soccer is the way the ball is kicked, and also the greatest spectacle in Soccer is kick. Nowadays, many players try to knuckle kick.

Well then what Knuckle Kick is? It is literally to kick without spin. It's one of the hardest shot for a keeper to stop because it's not spinning as mentioned above and so it starts moving all over the place.

Look at the video.

The ball moves from side to side and toward into net. Despite the ball fly about 30m, the ball doesn’t spin

Let me explain how to kick knuckle ball
First, we need to know where to kick the ball. The sweet spot is middle and bottom of the ball. And we should hit the ball strongly. It is very hard hit the sweet spot so many player practice a lot for perfect knuckle kick.

So how can knuckle kick make the ball moves from side to side?

This picture shows the flows of air each balls.

The upper image is spin ball and bottom image is non-spin ball.

As the picture, there is no vortex for spin-ball. but we can see vortex in non-spin ball.

The vortex calls Karman’s vortex.

If vortex occur, the atmospheric pressure in the vortex becomes lower
Object is pulled from low pressure to high pressure.
Therefore, when vortex occur above the ball the ball toward to upside, and when vortex occur bottom of the ball the ball toward to downside. This phenomenon make the ball shake

This is the trace of ball.

We can expect the trace of ball for normal kick, however, the trace of ball for knuckle kick move irregularly. It is hard to expect the trace.
This video shows how difficult blocking knuckle ball.