AIM: To determine the acceleration due to gravity on Earth using the drop ball technique.

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Session: May 2015                 Page |

International Baccalaureate Diploma Program (IBDP)

Session: May 2015

Physics HL Lab Report

Lab Report Title: Determining acceleration due to gravity.

Criteria Assessed:

  • Data Collection and Processing (DCP)
  • Conclusion and Evaluation (CE)

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International School, Singapore

AIM: To determine the acceleration due to gravity on Earth using the ‘drop ball’ technique.


Gravity is one of the four fundamental forces and on Earth, it pulls everything towards the center of the Earth.

According to Newton’s second law, since gravity is a force, it will cause any mass to accelerate. The objective of this experiment is to find the acceleration of any mass due to gravity on Earth. Since the Earth has an atmosphere, free fall of a mass is technically not possible due to the constant upward drag caused by wind. However, when the mass itself is many times denser than air, the effect of air resistance on its movement can be neglected. Hence, to find the acceleration due to gravity (g) in this experiment; all the students were given metal bob pendulum. Since a metal bob’s density is many times higher than air and its spherical shape is aerodynamic, the effect of air resistance on its downward descent could be ignored.

 where S = distance travelled, u = initial speed, t = time and a = acceleration.

For this experiment, the above equation modifies to. This is because the distance travelled is equal to the height from which the metal bob is dropped, initial velocity (u) is 0 and acceleration is equal to the acceleration due to gravity (g).

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Independent Variables:

  1. The height from which the ball was dropped.

Dependent Variables:

  1. The time taken for the ball to drop

Controlled Variables:

  1. Metal Bob – The same metal bob was used for all trials at all heights.
  2. Reaction time – One member of the group was responsible for timing all the trials so that delays due to his reaction time negate each other.
  3. The measuring tape – The same measuring tape was used to measure all heights.


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