S1 Science: Forces, Motion And Simple Machines (Paper 3 (challenge))

S1 Science: Forces, Motion and Simple Machines (Paper 3 (challenge))

2026-11-14

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Tutor Prep Guide · Speed and acceleration calculations, Newton laws and friction, lever moments, mechanical advantage of pulleys and inclines, plus efficiency and stopping distance

S1 Science: Forces, Motion and Simple Machines (Paper 3 (challenge))

This paper covers resultant force, balancing moments, efficiency, stopping distance, and why force and work cannot both be saved.

Direct answers　Subtract opposite forces, match force times arm on both sides, divide useful work by input work, and split stopping distance into thinking and braking parts.

01　Paper details (check answers afterwards)

Item	Detail
Questions	10
Suggested time	20
Difficulty mix	Foundation 3 · Intermediate 3 · Challenge 3 · Error redo 1
Chapter	Chapter: S1 Science: Forces, Motion and Simple Machines
Level	S1

02　Questions (10 items)

FoundationForces of 8 N to the right and 5 N to the left act on one box. What is the resultant?
FoundationA 30 kg child sits 1.2 m from a pivot. How far from the pivot must a 45 kg adult sit to balance?
FoundationWhat does mechanical efficiency mean?
IntermediateInput work is 200 J and useful work 150 J. What is the efficiency?
IntermediateA driver reacts in 2 s at 30 m/s. What is the thinking distance?
IntermediateA car at 20 m/s: the driver reacts for 1.5 s, then brakes to rest in 4 s. What is the total stopping distance?
ChallengeLifting a 1200 N load 1.5 m takes 1800 J. Pushing it up an ideal 5 m incline needs what force?
ChallengeA force-saving lever has moment arms in the ratio 4 to 1. What load can 150 N lift?
ChallengeTwo cars approach each other at 20 m/s and 15 m/s. How fast do they close on each other?
Error redoCan a force-saving machine also save work?

03　Answers and one-line notes

#	Answer	One-line note
1	3 N to the right	Opposite forces subtract, and 8 minus 5 gives 3 in the direction of the larger force.
2	0.8 m	The moments match, so 30 times 1.2 divided by 45 gives 0.8.
3	The ratio of useful work to input work, usually given as a percentage	Efficiency is always below one because friction always turns some energy into heat.
4	75 per cent	150 divided by 200 times 100 gives 75.
5	60 m	The car keeps its speed while the driver reacts, and 30 times 2 gives 60.
6	70 m	The thinking distance is 20 times 1.5 giving 30 and the braking distance is the mean speed 10 times 4 giving 40, so 70 in total.
7	360 N	The work stays the same on an ideal incline, and 1800 divided by 5 gives 360.
8	600 N	The moments match, and 150 times 4 gives 600.
9	35 m/s	Approaching speeds add, and 20 plus 15 gives 35.
10	No, an ideal machine trades distance for force so the work is unchanged, and a real one does extra work against friction	Work is force times distance, so the two cannot both fall.

04　What to do after marking

After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
Repeat the same item two days later; move to the next paper only when both attempts are correct.
Parents only need the answer and note columns; there is no need to explain every item.

For mechanics questions ask three things: whether the question asks for force, energy or time, whether units are already in m, s and N, and whether equilibrium or constant work is the premise.Tutor Registration →

Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.