Question

according to newtons first law of motion, an object in motion stays in motion. why does a ball that is thrown into the air ever
the unbalanced force of the earths gravity becomes greater than the force imparted by your hand.
a human arm is not very strong.
static friction stops the motion of the ball.
the ball is heavier than air and is pressed downward by the air.

Explanation:

Newton's first law states an object in motion stays in motion unless acted on by an unbalanced force. When a ball is thrown, gravity is the unbalanced force pulling it down. The force of gravity eventually overcomes the initial upward - force from the hand.

Answer:

The unbalanced force of the earth's gravity becomes greater than the force imparted by your hand.