Calculating Acceleration

 Our second (more complicated concept) in motion is to calculate acceleration:

Again, the first thing to keep in mind is to use SI units ("ms^-1" for the change in speed, and "s" for the time).

Note that we need to calculate the change in speed before we can calculate acceleration.

Calculating Speed from Acceleration

Sometimes, you will be asked to calculate the initial speed of something. This is one of the more difficult calculations using this equation.

For example,

When overtaking another driver, Sophie accelerates at 14.2 ms^-2 for 0.9s. She gets to a speed of 51.2 ms^-1. What speed was Sophie travelling at before she started to overtake the other driver?

STEP ONE: Calculate the change in speed

Δv    = a × Δt

        = 14.2 × 0.9

        = 12.78 ms^-1

STEP TWO: Calculate the initial speed

Δv    = final speed - initial speed

⇒ initial speed    = final speed - Δv

                            = 51.2 - 12.78

                            = 38.42 ms^-1