# Investigating How the Height From Which a Table Tennis Ball is Dropped Affects Its Bounce

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Investigating How the Height From Which a Table Tennis Ball is Dropped Affects Its Bounce

When a table tennis ball is dropped onto a surface it bounces. The

height of the bounce depends upon a number of factors; the pressure of

the air in the ball, the height from which it is dropped, its

material, mass and its temperature; the type of floor surface, its

temperature and its angle; and the acceleration due to gravity, the

temperature and the air resistance of the air that the ball will pass

through. In this experiment I will investigate the way in which the

height from which it is dropped affects the bounce of a table tennis

ball.

Planning

Objects that fall vertically, without air resistance, all have the

same acceleration at ground level on Earth, which is 9.80665m/s2. When

the air resistance force on a free-falling object is equal to the pull

of gravity, the object will reach its terminal velocity, i.e. it

cannot fall any faster. According to Newton's Second Law, mg - F = ma

(in this case, the resultant falling force of the ball minus the air

resistance force is equal to the mass of the ball multiplied by its

acceleration). The mass of the ball (m) will remain constant. As the

air resistance force (F) increases to the resultant force (mg), the

acceleration of the ball (a) decreases to nothing, so the ball

continues at its previous velocity without accelerating. Above a

certain height, therefore, I do not believe that the height from which

it is dropped will affect the height of a ball's bounce. However,

below this height, where the kinetic energy carried into impact will

vary between different drop heights, I believe the bounce height will

also vary.

As an object on Earth is dropped and bounces, the energy of that

object will undergo a series of transfers. It begins with

gravitational potential energy which is continually transferred to

kinetic energy as it accelerates towards the ground. Some energy is

lost in the ball's flight downwards and upwards due to air resistance