Determination of the acceleration due to gravity (g) by free fall.

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Determination of the acceleration due to gravity (g) by free fall

In this experiment we will determine the acceleration of gravity g by measuring the time of fight for balls dropped from a known height. I also verify that the acceleration due to gravity does not depend on the mass of the ball.

The falling body in this experiment will be a metal ball, which falls freely from the catch at the top of the apparatus to the pad below it. The apparatus is designed to record the time of flight for the ball. When the ball is in the catch, it forms part of an electrical circuit. When the ball is released, the circuit breaks and the timer start. The pad acts as a switch, such that when the ball hits it the timer is stopped.


Any object, which is moving, and being acted upon only be the force of gravity is said to be "in a state of free fall." This definition of free fall leads to two important characteristics about a free-falling object:

  • Free-falling objects do not encounter air resistance.
  • In the absence of air resistance, all objects in free-fall near the surface of the Earth will experience the same uniform acceleration


The force of gravity is the force at which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity, which is, directed "downward" towards the centre of the earth.


Acceleration is the rate of change of velocity.  On Earth, one force we can always count on is the ever present force of gravity pulling down on any object that has mass.  If gravity is the only force acting on an object, then we find the object will accelerate at a rate of 9.81m/s2 down toward the centre of the Earth (this is often rounded to 10m/s2).  


        Steel ball                   

                                                            Ball release mechanism



Controller box

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        Clamp stand

    Receptor pad



  • A free fall adaptor (ball release mechanism)
  • Receptor pad
  • Clamp stand
  • Electronic timing device
  • Metric stick
  • A steel ball


  1. Clamp the Ball Release Mechanism in the vertical position as illustrated in my diagram, at the desired height.

  1. Put the Ball Receptor plate on the table, positioning it beneath the Ball Release Mechanism.

  1. Make several test drops to insure that the ball will strike ...

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