Why does a ball move in your hand when net forces are 0?

AI Thread Summary
When a ball is held in hand and moved, the net force can be zero even while the ball is in motion. This occurs because the forces acting on the ball, including the push from the hand, gravity, and air friction, can balance each other out. While the ball accelerates upwards, the net force is not zero; it becomes zero when the ball moves at a constant velocity. The key point is that net force refers to the sum of all forces, not the absence of individual forces. Understanding this distinction clarifies how motion can occur even when net forces are balanced.
Matt Poirier
This is a more general and probably silly question, but if you have a ball in your hand and you move it upwards, the acceleration will be positive then after you move it at constant velocity, acceleration will be 0. However, how is net force is 0 when the ball is still moving? You are clearly still pushing on the ball, so does your hand's push and air friction cancel so net force is 0?

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Matt Poirier said:
You are clearly still pushing on the ball, so does your hand's push and air friction cancel so net force is 0?
You forgot gravity, but yes, the net force being zero is not the same as all individual forces being zero, just the sum of them.
 

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