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First teaching 2020

Last exams 2024

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Acceleration of Free Fall Experiment (CIE AS Physics)

Revision Note

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Katie M

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Acceleration of Free Fall Experiment

  • A common experiment to determine acceleration of a falling object which can be carried out in the lab

Apparatus

  • Metre rule, ball bearing, electromagnet, electronic timer, trapdoor

Measuring g, downloadable AS & A Level Physics revision notes

Apparatus used to measure g

Method

  • When the current to the magnet switches off, the ball drops and the timer starts
  • When the ball hits the trapdoor, the timer stops
  • The reading on the timer indicates the time it takes for the ball to fall a distance, h
  • This procedure is repeated several times for different values of h, in order to reduce random error
  • The distance, h, can be measured using a metre rule as it would be preferable to use for distances between 20 cm – 1 m

Analysing data

  • To find g , use the same steps as in the problem solving section
  • The known quantities are
    • Displacement s = h
    • Time taken = t
    • Initial velocity u = 0
    • Acceleration a = g

  • The equation that links these quantities is
    • s = ut + ½ at2
    • h = ½ gt2

  • Using this equation, deduce g from the gradient of the graph of h against t2

Sources of error

  • Systematic error: residue magnetism after the electromagnet is switched off may cause the time to be recorded as longer than it should be
  • Random error: large uncertainty in distance from using a metre rule with a precision of 1mm, or from parallax error

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Katie M

Author: Katie M

Expertise: Physics

Katie has always been passionate about the sciences, and completed a degree in Astrophysics at Sheffield University. She decided that she wanted to inspire other young people, so moved to Bristol to complete a PGCE in Secondary Science. She particularly loves creating fun and absorbing materials to help students achieve their exam potential.