Acceleration (Edexcel IGCSE Physics)

Acceleration

Rate of change in velocity

• Acceleration is defined as the rate of change in velocity

  • In other words, it describes how much an object's velocity changes every second

• The equation below is used to calculate the average acceleration of an object:

• Where:

  •  = acceleration in metres per second squared (m/s²)

  •  = change in velocity in metres per second (m/s)

  •  = time taken in seconds (s)

Formula triangle for acceleration, change in velocity and time

To use an equation triangle, simply cover up the value you wish to calculate and the structure of the equation will be revealed

• The change in velocity is found by the difference between the initial and final velocity:

• Where:

  •  = final velocity in metres per second (m/s)

  •  = initial velocity in metres per second (m/s)

• Therefore, the acceleration, or the rate of change in velocity, equation can be written as:

Speeding up and slowing down

• An object that speeds up is accelerating

• An object that slows down is decelerating

• The acceleration of an object can be positive or negative, depending on whether the object is speeding up or slowing down

  • If an object is speeding up, its acceleration is positive

  • If an object is slowing down, its acceleration is negative (also known as deceleration)

Examples of acceleration and deceleration

A rocket speeding up (accelerating) and a car slowing down (decelerating)