A TedEd by Erez Garty
In a 1997 soccer game between France and Brazil, Roberto Carlos set up for a 35m free kick with no direct path to the goal. Carlos kicked it wide of the players, seemingly out of bounds. But just before going out, it turned and went into the goal. How is this possible? Newton's 1st Law of Motion states that an object will move in the same direction and velocity unless a force is applied on it. So what force turned Carlos's ball? When he kicked the ball, he kicked it so that it turned on its axis. As the ball moved through the air, the air moved against the spin of the ball on one side while going with the spin on the other side. This created areas of low and high pressure, and the ball curved to the low pressure side, going into the goal. This is called the Magnus effect, first discovered in 1670 by Sir Isaac Newton while he was playing tennis. This can occur with other kinds of ball sports, and even frisbee. The type of kick is called a banana kick, and it is very hard. If you kick it too wide, it goes out; too far in, it won't get past the defenders. If it has too much spin, it won't go into the goal, and too little, it will go out. So is it possible to kick the ball so hard that it comes back? No, it will be slowed by the air, increasing its angle of deflection, and making it go in a perpetual spiral. And to do even that, you would need to give it 15 times as much spin as Carlos.
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