Why does it say that two forces in an action-reaction pair never act on the same body, when Newton's third law states that the force exerted by body A o B is equal and opposite to the force B exerts on A??? Are they both not acting upon the opposite body of each other? Could you expand upon what pg. 142 means on that statement.
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I do not understand why it mentions that an action-reaction pair never acts on the same body.
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If I push on the back of my car, I'm exerting a force on it, and if I push hard enough to overcome friction it will accelerate in the direction of my push.
If I do this while standing on a skateboard it's still possible that I might accelerate the car if my push is explosive enough, but it's far more likely that the reaction force exerted by the car on my hands will cause me to accelerate in the direction opposite my push.
It should be clear that I will accelerate in the direction opposite my push, so it can't be my push that accelerates me. A force is required in the direction of my acceleration. That force is the reaction to my push.