IP Physics Notes (Upper Secondary, Year 3-4): 6) Work, Energy & Power

Study guide30 Sep 2025, 00:00 ZUpdated 30 Nov 2025

Link work to energy transfers, apply conservation for height-speed swaps, and compute power and efficiency in IP Year 3-4 contexts.

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Q: What does IP Physics Notes (Upper Secondary, Year 3-4): 6) Work, Energy & Power cover?
A: Link work to energy transfers, apply conservation for height-speed swaps, and compute power and efficiency in IP Year 3-4 contexts.

Quick recap -- Energy tracks the ability to do work. When forces move objects they transfer energy, and the total energy in a closed system stays constant even as it changes form.

The core idea is simple: Work transfers energy when a force moves something.

Use it as a working check: Match the energy store to the situation: kinetic for speed, gravitational potential for height, elastic for springs, and power for energy transferred per second.

Then go one layer deeper: Use the sledge and conservation examples to practise writing the energy pathway, calculating work, allowing for losses, and checking efficiency or power units.

Keep your practice loop tight via our IP Physics tuition hub-it links each topic here to quizzes, diagnostics, and WA-style problem sets.

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These notes align with SEAB GCE O-Level Physics (6091) content used in IP programmes (exams from 2026).

Status: SEAB O-Level Physics 6091 syllabus (exams from 2026) checked 2025-11-30 - scope unchanged; remains the reference for these notes.

Energy Forms & Key Equations

Energy is the capacity to do work. SI unit: $\pu{J}$ ; energy is scalar.
Core mechanical stores:
- Kinetic: $E_k = \tfrac{1}{2} m v^2$

Reviewed by

Chee Wei Jie·Academic Advisor (Physics)

Question cue	Set up	Common trap
"Find the work done by this force"	Use $W = F s \cos \theta$ for that force only.	Using the full force when only its component acts along the motion.
"Find the speed after falling"	Equate lost $E_p$ to gained $E_k$ if losses are negligible.	Adding mass into both sides and then forgetting it cancels.
"Friction is present"	Put friction work on the loss side, or include it as negative work.	Treating friction as another stored energy instead of dissipated energy.
"Find efficiency"	Compare useful output to total input using energy or power consistently.	Mixing useful energy with input power in the same fraction.

Question data	First formula	Why it fits	Common trap
Work done and time	$P = W/t$	Power is work done per second.	Dividing by distance because work used a force and distance earlier.
Change in energy and time	$P = \Delta E/t$	The transferred energy is the work done on the system.	Using only kinetic energy when gravitational potential energy also changes.
Driving force and constant speed	$P = Fv$	In each second, distance travelled is $v$ , so work per second is $Fv$ .	Using $P = Fv$
Efficiency with input power	$P_\text{useful} = \eta P_\text{input}$	Useful output is a fraction of the total input rate.	Mixing useful energy with input power in the same fraction.

IP Physics Notes (Upper Secondary, Year 3-4): 6) Work, Energy & Power

Energy Forms & Key Equations

Principle of Conservation of Energy

Work Done

Worked Example: Sledge on a Ramp

Energy Conservation Applications

Energy Accounting Checkpoint

Power

Power formula selection checkpoint

Worked Example: Stair Climb Power

Efficiency

Practice Quiz

Internal Energy (Extension)

Key Takeaways

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