Throwing a Ball from the ground

We know that the Potential Energy is equal to Kinect Energy for any object Thrown from the ground. Not in a straight way of the words.

But in the a especific case when I use my my arms to throw a Ball, is the Potential Energy equals to Kinect one? I mn not using any mechanical advice.

Does the fact that I m using mechanical energy from my arms influentiate the throw?

2 Answers

If the only force on the object is gravity, then we can make a relation between the gravitational potential energy and the kinetic energy, that their sum is a constant.

$$GPE + KE = k$$

This does not hold when other forces are involved. In your case, it holds only for the time after the ball leaves your hand until the ball strikes some other object. Because of this, the mechanism of getting the ball into the air (arm, spring, rocket, volcano) doesn't matter.

Yes, the kinetic energy from your arm influences the throw. The speed with which you swing your arm determines the kinetic energy of the arm. When you finally throw it, this kinetic energy is converted to potential energy(of the ball) as the ball moves up in the air.

Note:Potential energy is not equal to kinetic energy, at least not always. However, their sum is constant. As one increases, other decreases.