Projectile Motion

Pronunciation: /prəˈdʒɛk taɪl ˈmoʊ ʃən/ ?

Projectile motion is the vertical motion of an object in a gravitational field given an initial velocity and height. The quadratic equation for projectile motion is:
where t represents time, a represents acceleration due to gravity, v0 represents the initial velocity, and h0 represents initial height. Since down is taken to be negative, acceleration due to gravity is a negative number.


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Manipulative 1: Projectile motion. Created with GeoGebra.

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  1. Jeff is standing on top of 20 foot tower. He throws a stick down at an initial velocity of -10 ft/s. Use -32 ft/s2 for the acceleration due to gravity. What is the equation for the vertical height of the stick? At what time does the stick reach the ground?

    1Identify the values of the constants.
    2Plug the constants into the equation. Simplify the equation.
    3Set the height to zero.
    4Apply the quadratic formula.
    5Since a negative solution does not make sense in this problem, the negative solution is extraneous solution. Discard the extraneous solution.
    Example 1

Cite this article as:

Projectile Motion. 2009-01-10. All Math Words Encyclopedia. Life is a Story Problem LLC.


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Revision History

2009-01-10: Initial version (McAdams, David.)

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