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My Question is about Newton's third law of motion

  1. Sep 8, 2016 #1
    Hello, I am Awais gul, a student of science subjects and learning the basic of Physics , chemistry and computer science.I have a Question about Newton's third law of Motion.

    Question : If we Throw a ball on a wall it goes back but if we throw a ball on sand why it does not go back?

    Newton's law states that: To every action, there is an equal but option reaction.

    In the law, there is no specific material then why It does not go back.
  2. jcsd
  3. Sep 8, 2016 #2


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    Although the laws of nature are always acting, there are other factors that affect motion. For example, a piece of paper can float upwards in the air, in apparent defiance of gravity. Gravity still acts on the paper, but there are other forces at work too.

    Why do you think a ball doesn't bounce very well on sand?
  4. Sep 8, 2016 #3
    Confusion arises because of vague wording in statements of laws, or misunderstanding the words. In your case, "action" does not mean "everything that happens"
    The experiment is, you are throwing a ball at something, wall or another ball or whatever. When the ball hits the object, the ball exerts a force on the object. You can call this force the "action". The object exerts an equal force on the ball, in the opposite direction. This force can be called the "reaction. Newton's law is talking about these two forces. The "reaction" is not "going back". The reaction is, the equal force in the opposite direction. Of course, it does not matter which one you call the action and which one the reaction.

    To add, as Perok says above, you must be mindful of other forces acting on each object in question. All the forces acting on an object together determine what "happens" to that object.
  5. Sep 8, 2016 #4


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    Look up the difference between elastic and inelastic collisions.
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