Kinetic Energy and Velocity of a Dropped Ball

[Ki-nana18]

Homework Statement

A ball at the top of its drop has 15 J of potential energy, neglecting air resistance, what is the kinetic energy at the bottom of the drop? What is the velocity?

Homework Equations

The Attempt at a Solution

Because the problem is asking for the kinetic energy and velocity at the bottom of the drop, I guessed that both the kinetic energy and velocity would be 0.

 

[pgardn]

Homework Statement

A ball at the top of its drop has 15 J of potential energy, neglecting air resistance, what is the kinetic energy at the bottom of the drop? What is the velocity?

Homework Equations

The Attempt at a Solution

Because the problem is asking for the kinetic energy and velocity at the bottom of the drop, I guessed that both the kinetic energy and velocity would be 0.

Energy is conserved. So you must have 15 J of energy at every position during the drop.
What is the equation for kinetic energy? And were you given mass the mass of the ball?

 

[Ki-nana18]

The equation for kinetic energy is KE=(1/2)(m)(v²). I was not given the mass of the ball.

 

[pgardn]

The equation for kinetic energy is KE=(1/2)(m)(v²). I was not given the mass of the ball.

Unless I am missing something then you need that... the mass of the ball.

Unless you were given the height from which the ball was dropped (presumably from rest)?

You could have a larger mass dropped from small height, or a smaller mass dropped from a higher position, both of which could yeild 15 J of mechanical energy... But would give you diff. answers if you wanted to find v from kinetic energy.