Motion and forces Study Guide

Acceleration is a measure of how quickly an object's velocity changes. It is a vector quantity, meaning it has both magnitude and direction. A positive acceleration indicates an increase in velocity (speeding up), while a negative acceleration (often called deceleration) indicates a decrease in velocity (slowing down). The standard unit for acceleration is metres per second squared (m/s²). The equation for calculating average acceleration is given by: acceleration = (final velocity - initial velocity) / time taken. This can be written as a = (v - u) / t, where 'a' is acceleration, 'v' is final velocity, 'u' is initial velocity, and 't' is the time over which the change occurs. Accurate application of this formula requires consistent units for all quantities. For instance, if velocity is in m/s and time in s, acceleration will be in m/s².

Speed is a measure of how fast an object is moving, calculated as the distance travelled per unit of time. Different objects and phenomena have characteristic speeds that are useful to recall for comparison and problem-solving. For instance, the speed of sound is significantly faster than typical human movement, while wind speeds can vary greatly but are generally much lower than the speed of light. Knowing these typical values helps develop an intuitive understanding of scale in physics and everyday situations.