DSE Physics: Work, Energy and Power — Tutor Lesson Plan (W = Fs, KE, PE, P = W/t)

2026-10-27

Tutor lesson-prep guides · Secondary physics

Students memorise W = Fs then freeze on a slope. Three ideas carry the lesson: force and displacement must share a direction, energy only changes form, and power is energy over time.

Objectives — the student can decide whether a force does work, compute with W = Fs, kinetic energy and mgh, and find power from P = W/t.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Second law	2 kg with 10 N nett	5 m/s²
Units	What is one joule?	1 N m
Speed	Convert 72 km/h	20 m/s

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-10 min	What counts as work	Force and displacement in the same direction	Sort five cases
10-26 min	W = Fs	20 N over 3 m	Two alone
26-44 min	Energy exchange	KE and PE trading	Free-fall speed
44-54 min	Power	P = W/t	Two questions
54-57 min	Answer format	Formula, substitution, unit	Rewrite one
57-60 min	Exit check	Three questions marked	Finish alone

03 Teaching script (read it out)

Scene 1: Work needs force along the displacement

W = Fs, but only the component along the motion counts.
Carrying a book horizontally: the force is upward, the motion forward, so no work is done.
20 N over 3 m gives 60 J.

Student judges pushing a wall that does not move: no work, s = 0.

Scene 2: Energy changes form, never disappears

Falling: lost potential energy becomes kinetic, mgh = half m v squared.
2 kg falling 3 m with g = 10 stores 60 J, landing at about 7.75 m/s.
With friction, part becomes heat and the total is still conserved.

Note: the energy route avoids acceleration, but say where the lost energy went.

Scene 3: Power is energy per second

P = W/t. 60 J in 4 s is 15 W.
The same work done faster is more power; power is not force.

Student computes lifting 2 kg by 3 m in 4 s: 15 W.

04 Question types and worked steps

Type	Example	Steps	Answer
Work	20 N over 3 m	W = Fs	60 J
Kinetic energy	2 kg at 4 m/s	half m v squared	16 J
Potential energy	2 kg, 3 m, g = 10	mgh	60 J
Power	60 J in 4 s	P = W/t	15 W

Sanity check (teach this): The energy route and kinematics must agree: 2 kg from 3 m gives 7.75 m/s either way.

05 Independent practice (3 questions)

Question	Answer	What to watch
10 N over 5 m	50 J	W = Fs
3 kg at 6 m/s	54 J	Half times 3 times 36
1.5 kW for 20 s	30 000 J	W = Pt

06 Common mistakes and what to say

Mistake	Student writes	Say this
Multiplying force by motion in another direction	counts carrying a book as work	Use the component along the motion.
Missing the half	writes m v squared	Kinetic energy is half m v squared.
Weight in place of mass	substitutes 20 N into mgh	m is in kg.
Power in joules	P = 15 J	Power is in watts.

07 Homework (paper, section and question numbers)

Secondary physics chapter index — Use the three questions on this page

08 Exit check (last 5 minutes)

Question	Answer	Decision
10 N over 5 m	50 J	All right: move to electricity
3 kg at 6 m/s	54 J	One wrong: re-teach energy
1.5 kW for 20 s	30 000 J	Two wrong: repeat scene 3

09 Tutor FAQ

g as 9.81 or 10?

Use what the paper gives; state the value.

What about friction?

Input equals output plus heat.

Link to momentum?

Energy is scalar, momentum vector; collisions need both.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.