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A bouncing ball captured with a stroboscopic flash at 25 images per second. Note that the ball becomes significantly non-spherical after each bounce, especially after the first. That, along with spin and air-resistance, causes the curve swept out to deviate slightly from the expected perfect parabola. Spin also causes the angle of first bounce to be shallower than expected. As a ball falls freely under the influence of gravity, it accelerates downward, its initial potential energy converting into kinetic energy. On impact with a hard surface the ball deforms, converting the kinetic energy into elastic potential energy. As the ball springs back, the energy converts back firstly to kinetic energy and then as the ball re-gains height into potential energy. Energy losses due to inelastic deformation and air resistance cause each successive bounce to be lower than the last. The image is of a child's ball about the size of a tennis ball: image by Michael Maggs, 29 September 2007; edit by Richard Bartz
You approach me carrying a book
The instructions you read carry me back beyond birth
To childhood and a courtyard bouncing a ball
The town is silent there is only one recreation
It’s throwing the ball against the wall and waiting
To see if it returns
One day
The wall reverses
The ball bounces the other way
Across this barrier into the future
Where it begets occupations names
This is known as the human heart a muscle
A woman adopts it it enters her chest
She falls from a train
The woman rebounds 500 miles back to her childhood
The heart falls from her clothing you retrieve it
Turn it over in your hand the trademark
Gives the name of a noted maker of balls
Elastic flexible yes but this is awful
You say
Her body is limp not plastic
Your heart is missing from it
You replace your heart in your breast and go on your way
The concrete map of unknown places: image by di de, 22 January 2006