Kinematics: motion problems solved with visible reasoning

Kinematics is five equations and one decision: which quantity is missing. Noeta trains that decision, then reviews it days later.

What this covers

  • Displacement, velocity, acceleration
  • The SUVAT equations
  • Motion graphs and their gradients
  • Free fall
  • Projectile motion in two dimensions

Worked example

Problem

A car accelerates from rest at 3 m/s² for 8 s. How far does it travel?

  1. 1
    List the knowns
    u = 0, a = 3 m/s², t = 8 s, s = ?
  2. 2
    Choose the equation
    s = ut + ½at² uses exactly those variables.
  3. 3
    Substitute
    s = 0 + ½ × 3 × 8² = ½ × 3 × 64.
Answer: 96 metres

Mistakes that cost marks

  • Using a SUVAT equation when acceleration is not constant.
  • Mixing horizontal and vertical components in projectile problems.
  • Forgetting that g acts downward, so signs matter.

Questions students ask

How do I choose the right SUVAT equation?

Write down the four known quantities and the unknown; exactly one equation omits the variable you do not have.

Practise mechanics until it sticks

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