Work, Energy and Power summary

Key learning points

• Work $=Fd$ for a constant force along the displacement (use the component along the motion).
• KE $=\frac{1}{2}mv^2$; GPE $=mgh$; friction does negative work.
• Power $P=Fv$ at constant speed when $F$ drives against resistance.
• Track energy losses stated in the question.

Worked example 1 — Power

Constant speed $20\,\mathrm{m\,s^{-1}}$ against $300\,\mathrm{N}$ resistance. Driving power?

Working

At constant speed, driving force equals resistance, so $P=Fv$.

Worked example 2 — Work for a constant force along the displacement (use

Use this method from the Work, Energy and Power sheet: Work $=Fd$ for a constant force along the displacement (use the component along the motion).

Working

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

Worked example 3 — KE ; GPE ; friction does negative work

Use this method from the Work, Energy and Power sheet: KE $=\frac{1}{2}mv^2$; GPE $=mgh$; friction does negative work.

Working

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

Worked example 4 — Power at constant speed when drives against resistance

Use this method from the Work, Energy and Power sheet: Power $P=Fv$ at constant speed when $F$ drives against resistance.

Working

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

Worked example 5 — Track energy losses stated in the question

Use this method from the Work, Energy and Power sheet: Track energy losses 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.