Edexcel International A Level Maths: Mechanics 1

Revision Notes

1.1.3 Derived Units

Test Yourself

Derived Units

What are derived units?

  • Derived units for quantities such as velocity, acceleration and force etc. are combinations of S.I. units
    • Speed or Velocity = distance ÷ time = m/s or ms-1 (Velocity is just speed with direction)
    • Acceleration = velocity ÷ time = ms-1 /s = m/s2 or ms-2
    • Weight or Force = mass x acceleration = kgms-2 or N (N = Newtons)

    1-1-3-diagram-1

Worked example

(a)
Convert the following into S.I. units

    i)      72 km h-2      ii)  50 cm per minute      iii)  14 g cm-3

1-1-3-worked-solution-a

(b)
A cyclist takes 15 minutes to travel 2.54 km. Calculate the average speed in m s-1?

1-1-3-worked-solution-b

Exam Tip

  • Watch out for exam questions using non S.I. units such as feet and inches or miles per hour.
  • Make sure you are confident converting between these derived units,
  • Remember speed is velocity without direction and weight is a force measured in Newtons, not a mass measured in kg.
  • If you ever forget a formula, use the units it is measured in to figure it out,

    e.g. m/s = metres ÷ seconds = distance ÷ time = velocity.

You've read 0 of your 0 free revision notes

Get unlimited access

to absolutely everything:

  • Downloadable PDFs
  • Unlimited Revision Notes
  • Topic Questions
  • Past Papers
  • Model Answers
  • Videos (Maths and Science)

Join the 80,663 Students that ❤️ Save My Exams

the (exam) results speak for themselves:

Did this page help you?

Amber

Author: Amber

Amber gained a first class degree in Mathematics & Meteorology from the University of Reading before training to become a teacher. She is passionate about teaching, having spent 8 years teaching GCSE and A Level Mathematics both in the UK and internationally. Amber loves creating bright and informative resources to help students reach their potential.