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The Screwball

(Click the Play Ball button in the lower left corner if the baseball isn't already on the screen.)

Let's throw our third pitch, the Screwball.

  • HOW DOES A SCREWBALL DIFFER FROM A CURVEBALL?

    To find out, watch the baseball as you move the Spin slider back to the right. Stop a few places along the way, both to the right of Fastball and to the left of Fastball.

  • WHAT DO YOU SEE HAPPENING?

    Yes, the Screwball rotates in the opposite direction of the Curveball. To note other changes, be sure you have clicked on Surface Pressure in the Plotter Control Panel and watch the graph as you slide the Spin slider from far left to far right and then back. Do this several times.

  • WHAT HAPPENS TO THE GREEN AND YELLOW LINES?

    They change positions. This means that the high pressure side of the ball is reversing. Keep sliding the Spin slider back and forth and watch the Side Force bar.

  • HOW DO THE FORCE READINGS CHANGE?


    They go from positive values for the Curveball to negative values for the Screwball. This means that the Side Force being exerted is changing directions.

  • MAKE A PREDICTION ABOUT THE PATH OF THE SCREWBALL

    Now click on Ballpark button on the Plotter Control Panel and view the path of your pitch to check your prediction. Were you right?

    It's time for the next lesson - Baseball and Altitude
    Or go back to Baseball Lessons

    Please send any comments to:
    Curator:     Tom.Benson@grc.nasa.gov
    Responsible Official: Kathy.Zona@grc.nasa.gov