Acceleration (Cambridge O Level Physics)

• Acceleration is defined as the rate of change of 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:
  • a = acceleration in metres per second squared (m/s²)
  • Δv = change in velocity in metres per second (m/s)
  • Δt = time taken in seconds (s)

• The change in velocity is found by the difference between the initial and final velocity, as written below:

change in velocity = final velocity − initial velocity

• Where:
  • v = final velocity in metres per second (m/s)
  • u = initial velocity in metres per second (m/s)

• The equation for acceleration can be rearranged with the help of a formula triangle as shown:

Acceleration equation triangle

Equation triangle for the change in velocity, acceleration, and change in time

Speeding Up & 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 (sometimes called deceleration)

Acceleration and deceleration

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