Newton's Laws of Motion summary

Key learning points

• First law: constant velocity unless a resultant force acts.
• Second law: resultant force equals mass times acceleration.
• Third law: interaction forces are equal and opposite on different bodies.
• Use the value of $g$ stated in the question.

Worked example 1 — F=ma

Resultant force $15\,\mathrm{N}$ on $3\,\mathrm{kg}$. Acceleration?

Working

$a=F/m$ in the direction of the resultant.

Worked example 2 — First law: constant velocity unless a resultant force

Use this method from the Newton's Laws of Motion sheet: First law: constant velocity unless a resultant force acts.

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 3 — Second law: resultant force equals mass times accelerat

Use this method from the Newton's Laws of Motion sheet: Second law: resultant force equals mass times acceleration.

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 4 — Third law: interaction forces are equal and opposite

Use this method from the Newton's Laws of Motion sheet: Third law: interaction forces are equal and opposite on different bodies.

Working

Each key learning point matches a question type on the printable worksheet.

Worked example 5 — Use the value of stated in the question

Use this method from the Newton's Laws of Motion sheet: Use the value of $g$ stated in the question.

Working

Each key learning point matches a question type on the printable worksheet.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.