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Soccer

 

Overview

The score is tied, with only three minutes left in the game. To win, you need to think and move fast to control the ball, get it down the field, and shoot it past the goalie. Can science help? Soccer (or football, as the game is known outside the United States) requires lots of training and practice. But while training books may not mention anything about momentum, collisions, or Newton's third law of motion, every move a soccer player makes involves physics. How? When your foot, thigh, knee, chest, or forehead acts on the soccer ball, the ball reacts. Players need to know when to best use heading, dribbling, passing or power kicking, feinting, trapping, swerving, or shooting. For example, a passing kick uses the inside of the foot and provides the largest surface area to contact the ball. This gives you better control of where the ball goes, but with your leg turned out, you can't swing it with maximum force. The ball won't go as far as it would with a power kick, where your knee points in the same direction the ball goes. That's why you need the force of a power kick to drive the ball down the field. And remember that to have more control, use the laces of your shoe rather than your toes to get a bit more surface area. It won't do much good to get the ball down the field if it doesn't go where it's supposed to! How big you are and how fast you're moving when you make contact with the ball is an important factor, too. Why? Your momentum - whether you're running toward the ball when you kick it or toward the goal when someone passes it to you - can move that ball down the field at very high speeds. Your mass (which is related to your body weight) multiplied by your velocity, or motion in a particular direction, equals a lot of momentum. When your body collides with the ball, you share your momentum with it. The more momentum the ball gets from you, the faster and farther it will move. The bigger you are and the faster you're moving, the greater your momentum will be, and the more momentum you will have to share with the ball. Of course, this all looks very different to the defending goalie. The goalie must be ready to absorb all the momentum of the ball you just kicked when it collides with her or his body. But if you do your job right, that person won't feel a thing - the net will.

Activity

What factors determine how high or how far a ball goes when kicked? To find out, gather some friends to kick a soccer ball and take measurements. Materials
  • school athletic field or park
  • paper
  • pencils or pens
  • masking tape
  • soccer ball
  • tape measure
1. Divide into two groups. Group A will kick the ball; Group B will observe the kicks and measure the distance the ball travels. 2. Create a table to record your observations and conclusions. 3. Use masking tape to mark the line where each kick will take place and to mark off the field at 5 - meter (16') increments. 4. Each member of Group A will kick the ball six times - three times with a running kick and three times with a standing kick. 5. A member of Group B should write down how far the ball traveled in the air (that is, where it landed, not where it stopped rolling). Members of Group B can also estimate the angle at which the ball was kicked and note that in the table. 6. Switch group roles and repeat steps 4 - 5. 7. Average the running kick distances and the standing kick distances for all the kickers. Questions
  1. What effect does the condition of the playing field (dry, muddy, natural, or plastic) have on the momentum of the kickers and the ball? What effect do cleats have on the kickers' momentum?
  2. How does a kicker's weight affect the results?
  3. Based on the results recorded in your table, can you determine the kick angle that produces the longest distances?

Resources

    Ditchfield, M. & Bahr, W. (1988) Coaching soccer the progressive way.
    Englewood Cliffs, NJ: Prentice-Hall.
    Gonick, L. & Huffman, A. (1991) The cartoon guide to physics.
    New York: Harper Collins.
    Yeagley, J. (1994) Winning soccer. Indianapolis: Masters Press.
    The Center of Excellence for Science and Mathematics Education:
    http://192.239.146.18
    SoccerCity: 2000+ links to soccer sites:

    http://nettvik.no/sportsholmen/soccercity/

    Soccer - The International Soccer Cybertour:

    http://www.cybergoal.com/soccer

    3M Learning Software: What's the secret? (vol 3).
    CD-ROM for Macintosh or Windows. (800) 219-9022.
    American Youth Soccer Organization (AYSO)
    5403 West 138th St
    Hawthorne, CA 90250
    (800) USA-AYSO
    http://www.ayso.org