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Newton's Second Law

The acceleration of an object equals the net force acting on the object divided by the object’s mass.

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Field Goal Physics

Field Goal Physics

Credit: Public domain
Source: http://commons.wikimedia.org/wiki/File:US_Navy_051008-N-9693M-018_U.S._Naval_Academy_Midshipmen_kicker_Joey_Bullen_kicks_a_field_goal_with_4-10ths_of_a_second_left_in_the_game_against_Air_Force_for_three_points.jpg
License: CC BY-NC 3.0

He aims, he kicks, he scores a field goal! He may not know it, but he’s also applying an important law of physics: Newton’s second law of motion.

The Back Story

  • Newton’s second law states that the acceleration of an object equals the net force acting on the object divided by the object’s mass. An object accelerates whenever it undergoes a change in velocity, that is, a change in the speed or direction of motion.
  • Credit: Nikos Koutoulas
    Source: http://www.flickr.com/photos/33284937@N04/7507679046/
    License: CC BY-NC 3.0

    When you push on the gas pedal in your car, the car accelerates forward [Figure2]

  • Watch this video to see how Newton’s second law applies to kicking field goals in football: http://www.nbclearn.com/nfl/cuecard/50974

Can You Apply It?

Learn more about Newton’s second law and kicking a football at the link below. Then answer the questions that follow.

  1. In kicking a field goal in football, how is force applied to the ball? How much force is applied to the ball by an NFL kicker?
  2. What is an impulse? How is it calculated?
  3. How does a larger impulse affect the football when it is kicked?
  4. Footballs used in the American NFL and the Canadian CFL differ in mass. What is the mass of each football? How does the mass of a football affect its motion when it is kicked?
  5. What is inertia? How does the mass of an object such as a football relate to its inertia?
  6. How is the acceleration of an object calculated if you know its mass and the amount of force that is applied to it?
  7. If a net force of 300 N is applied to both an NFL football and a CFL football, what is the acceleration of each ball?

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