Acceleration and deceleration
Physics Narrative for 11-14
Please take care with
acceleration. This note explains some concerns.
acceleration is used to describe motion which changes. It is common to use acceleration to mean speeding up and the word deceleration to mean slowing down. Strictly speaking, however,
acceleration describes both types of motion. Speeding up might be referred to as
positive acceleration and slowing down as
negative acceleration. However, raising this point may confuse pupils at this level, with little addition to their understanding. Later in their studies of science, pupils will be introduced to a more formal definition of acceleration in terms such as:
acceleration = change in speedtime for change
(units of acceleration: metresecond in each second, or metresecond2).
If they are introduced to an even more precise definition, it will be that acceleration is change of velocity each second. Pupils will also measure accelerations and resultant forces and relate them to each other. Sir Isaac Newton, in his second law of motion, saw that the greater the resultant force, the greater will be the resulting acceleration of a fixed mass. This finding is summarised in the relationship:
Fm = a
Where F is force in newton; m is mass in kilogram; a is acceleration in metresecond2.