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Force exerted on Earth by accelerating ball

  1. Sep 6, 2015 #1
    1. The problem statement, all variables and given/known data
    When a ball is bounced from the ground, the earth exerts the force necessary to reverse its velocity. Is there a simultaneous force exerted on the earth? If there is one, why don't we perceive any acceleration of the earth?

    2. Relevant equations
    Newton's second law: net F=ma, F and a being vectors
    Newton's third law: all forces act in pairs, equal and opposite


    3. The attempt at a solution
    So when the ball is say released from my hand it heads toward the ground. Now the ball's velocity is changing and therefore is accelerating. Its speed is increasing but its direction is in the downward direction. Now the acceleration of the ball is due to the force of attraction of earth. That makes sense to me. However, when the ball hits the ground, its exerts a force on the ground (normal force') and the ground exerts an upward force (normal force). The ball has another force acting on it, its weight and it exerts a force (weight') on the earth. But I'm confused which force causes the ball to bounce back in the opposite direction, causing it to accelerate it upwards. I know that the earth does accelerate but its effect is trivial since mass of earth is large relative to the ball.
     
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  3. Sep 6, 2015 #2

    Orodruin

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    In which direction is the net acceleration during the bounce? The answer to this question should give you a hint as to what is the force responsible.
     
  4. Sep 6, 2015 #3
    The net acceleration is downwards because of gravity and then upwards due to normal force. So is this the contact force from the ground (earth) that causes the ball to change its velocity in upward direction? That's what I'm thinking
     
  5. Sep 6, 2015 #4

    Orodruin

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  6. Sep 6, 2015 #5
    This makes sense to me now. And when the ball and ground come in contact, the ground DOES accelerate but is very hard to notice due to earth's mass. The reason I see the ball accelerate upward is because its mass is lighter with respect to the ground (the earth).
     
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