Calculating Uniform Acceleration (Edexcel IGCSE Physics)

This is an example of an equation that cannot be rearranged with a formula triangle. It is really important that you learn to rearrange equations without the help of a triangle for your exam. 

To rearrange any equation, follow these simple rules:

• What ever you do to the equation, you must do to both sides

• To undo an operation, perform the opposite operation

  • To undo a subtraction, you must add (and vice versa)

  • To undo a multiplication, you must divide (and vice versa)

  • To undo a square, you must square root (and vice versa)

Always show your working out, there is usually a mark awarded for rearranging an equation in an exam question. 

A car accelerates steadily from rest at a rate of 2.5 m/s² up to a speed of 16 m/s.

Calculate how far the car moves during this period of acceleration.

Answer:

Step 1: List the known quantities

• Initial speed,  

  • Because the car starts from rest

• Final speed,

• Acceleration,  

Step 2: Identify and write down the equation to use

• The question says that the car 'accelerates steadily' - so the equation for uniform acceleration can be used:

Step 3: Rearrange the equation to work out the distance moved

• Subtract  from each side

• Divide both sides by 

Step 4: Substitute known quantities into the equation and simplify where possible

Writing out your list of known quantities and labelling the quantity you need to calculate is really good exam technique. It helps you determine the correct equation to use, and sometimes examiners award credit for showing this working.