DSE Physics: Force and Motion — Tutor Lesson Plan (Newton laws, F=ma, equations)

2026-10-27

Tutor lesson-prep guides · Secondary physics

Students memorise F = ma and then misuse it at constant velocity. Three questions separate the cases: is the net force zero, is there acceleration, which equation applies.

Objectives — the student can link a zero net force to constant velocity, apply F = ma with the net force in newtons and mass in kilograms, and choose the correct equation of motion.

01 Prerequisites (3-minute check)

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

Skill	Quick check	Pass mark
Vectors	Combine 3 N east and 4 N north	5 N, about 53 degrees
Units	Which base units define the newton?	kg m s^-2
Speed vs velocity	State the difference	Velocity has direction

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-10 min	Three cases	Zero net force, non-zero net force, find displacement	Sort five questions
10-24 min	First law	Inertia and constant velocity	Explain two examples
24-40 min	F = ma	2 kg with 10 N nett	Two alone
40-52 min	Equations	v = u + at, s = ut + half a t squared	Two alone
52-57 min	Answer format	List givens, then choose	Rewrite one answer
57-60 min	Exit check	Three questions marked	Finish alone

03 Teaching script (read it out)

Scene 1: Zero net force means constant velocity

First law: with no net force an object stays at rest or moves at constant velocity.
Constant velocity does not mean no forces; it means the forces cancel.

Student states the net force at constant velocity: zero.

Scene 2: F = ma uses the net force

A 2 kg object with 10 N nett force accelerates at 10 / 2 = 5 m/s².
Use the net force, not one applied force, and mass in kilograms, never weight in newtons.

Student identifies which forces add and which cancel.

Scene 3: Choose the equation that misses one quantity

Five quantities: u, v, a, t, s. Each equation omits one, so pick the one you can solve.
u = 0, a = 2, t = 3 gives v = 6 m/s and s = 9 m.

Note: list givens and the unknown before choosing.

04 Question types and worked steps

Type	Example	Steps	Answer
Acceleration	2 kg, 10 N nett	a = F / m	5 m/s²
Final velocity	u = 0, a = 2, t = 3	v = u + at	6 m/s
Displacement	same data	s = ut + half a t squared	9 m
Net force	lift descending at constant speed	Net force is zero	0 N

Sanity check (teach this): Constant velocity always means zero net force; a non-zero net force with constant velocity means a force was left out.

05 Independent practice (3 questions)

Question	Answer	What to watch
5 kg with 15 N nett	3 m/s²	Divide force by mass
u = 5, a = 3, t = 4	17 m/s	v = u + at
u = 0, a = 4, t = 5	50 m	Half times 4 times 25

06 Common mistakes and what to say

Mistake	Student writes	Say this
Weight used as mass	substitutes 20 N for m	Mass in kg, weight in N.
One force treated as nett	uses only the push	Add and subtract all forces.
Wrong equation	uses the equation without v to find v	List the five quantities first.
Wrong unit	a written as 5 N	Acceleration is m/s².

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
Net force at constant velocity	Zero	All right: move to energy
5 kg with 15 N nett	3 m/s²	One wrong: re-teach F = ma
u = 0, a = 4, t = 5	50 m	Two wrong: repeat scene 3

09 Tutor FAQ

Memorise the equations?

Yes, but learn the omit-one method first or they get mixed up.

g as 9.8 or 10?

Use what the paper states; DSE usually uses 9.81.

Link to the energy chapter?

Energy conservation gives a second way to check the same answer.

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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.