The Bouncing Ball Experiment

A Ball Drops:

Energy is needed to do everything.  Light, sound, movement and heat are all examples of things that need energy to exist.  Energy is defined as the ability to do work – to make something happen e.g. to move something.  If something can apply a force over a distance, it has energy. The easiest way to detect energy is when it is changed from one form to another.  To then measure how much energy is present, we can measure the amount of work done whilst the transformation is occurring.

An object can store energy as a result of its position.   When a ball is held at a height, it stores energy.  This stored energy is referred to as potential energy.  It is called potential energy because the ball has the potential to drop (converting the potential energy into kinetic/movement energy), if it is let go of.  The higher the ball is from the ground, the more kinetic energy it will need to fall back down.  The kinetic energy is converted from the Gravitational Potential Energy the ball has when it is elevated. Gravitational potential energy is the energy stored in an object as the result of its vertical position.  The ball falls to the ground due to the force of gravity by converting the gravitational potential energy (GPE) into kinetic energy needed for the ball to move.  The higher the ball is elevated, the more GPE it has.   As the ball falls down, its GPE falls as it is converted into kinetic energy.  The amount of kinetic energy stored in the ball increases as more and more of the gravitational potential energy is converted.  The more kinetic energy the ball has stored, the faster it moves.

Apparatus Needed:

One Tape measure

One Caliper

One set of electronic scales

One standard size ping-pong ball

Two Metre-long Rulers

*There must also be access to a staircase that rises to at least five cm (500cm) from the ground.  

Diagram:

Method:

A tape measure was used to measure where on the stairs the height we desired from floor to staircase was.  We found where we should stand on the stairs for measuring all the heights from 50cm to 500cm with 50cm gaps in-between each.  Next, the ping-pong ball was measured and weighed so that when it came to doing energy calculations relating to kinetic energy or work done (energy transfer), I would be able to put numbers into them, and form conclusive results.  Two metre rulers were stood on top of each other in front of the 50cm mark and held firmly in place by two people so that they were not slanting or leaning against the staircase. The ping-pong ball was taken to the place on the staircase we had measured to be 50cm from the ground.   The ball was dropped from this height alongside the metre rulers with no force exerted on it.  A different person standing on the ground directly in front of the metre rulers noted the height of the bounce.  This was done three times and an average bounce height for a 50cm drop height was found.  The whole experiment was then repeated using different drop heights of 100cm, 150cm, 200cm, 250cm, 300cm, 350cm, 400cm, 450cm and 500cm. The same person dropped the ping-pong ball each time and the same person noted the bounce height each time.  The same ping-pong ball was used for each experiment.  For each drop height, an average was found and the results recorded.

I had enough evidence that I could study to work out why my graph was a curve instead of a straight line.  I also feel that I had enough evidence to back up my conclusion.  All my results did follow a pattern.  I didn’t have any unexplainable results because I took enough tests and averages to even out any slight glitches in the pattern.

If I could extent this experiment even further, I think I would carry out the same experiment with a different ball.  This way, I could relate the results I have gained with a ping-pong ball with results with say a tennis ball.  The pressure inside a tennis ball is different to that of a ping-pong ball.  It would be interesting to see what difference this makes to the results.  Also, the tennis ball is made of a different material and is squashy.  A tennis ball has a bigger surface area than a ping-pong ball because it is bigger.  I predict that air resistance has more effect on a tennis ball than it does on a ping-pong ball.  Therefore I predict that the graph will look very similar in direction, but the graph for the tennis ball will start to curve more dramatically quicker than the ping-pong ball does.  This is because the tennis ball will be losing more energy due to air resistance.