The force of the players head on the ball is 1.5N upward, What is the force of the ball on the players head?

The force is 1.5N acting downward or - 1.5N.

Why?

To answer this question, we need to remember the Newton's Third Law. This Law states that for every force applied upon an object, there is an equal force acting in the opposite direction. This Law is also called "action-reaction Law".

So, if the force of the players heads applied on the ball is equal to 1.5N (upward), the force applied by the force on the players heads will be exactly equal, but with opposite direction, or - 1.5N (downward).

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