Science and Technology K–6 · Year 4

Dragging a shoe with a spring balance: measuring friction in newtons

Science understanding: Physical sciences

Practical, model not builtLow risk

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The idea

Friction is a force that can be measured, it grows when the object presses harder on the surface, and it depends on which two surfaces touch.

What you need

spring balance, 0 to 10 N (1 kg), with a hook
1 school shoe (about 400 g) with a loop of string through the laces
4 masses of 100 g (or 100 g bags of rice)
surfaces: carpet, tiles, a wooden bench, a sheet of sandpaper
kitchen balance to weigh the shoe

How to do it

Weigh the shoe and record its mass in grams. Convert to weight in newtons (mass in kg x 9.8).
Hook the balance to the string and pull the shoe slowly along the tiles at a steady speed. Read the force while it slides, not the jerk when it starts. Repeat three times and take the mean.
Repeat on carpet, wood and sandpaper.
Back on the tiles, put a 100 g mass in the shoe and pull again; add 100 g at a time and repeat, up to 400 g extra. If the balance nears 10 N before it starts to slide, stop adding mass.
Draw two graphs: friction force against surface (columns) and friction force against total weight on the tiles (line).
For each surface, divide the sliding friction by the shoe's weight to get the friction coefficient.

What you should see

A 400 g shoe weighs 3.9 N; with 400 g extra the shoe and load weigh 7.8 N, so the starting pull stays inside the balance's 10 N range unless the friction coefficient is above about 1.3. Friction differs from surface to surface, and the order is the learner's result. On any one surface it rises close to a straight line with the weight in the shoe, so doubling the total weight roughly doubles the force, and the coefficient (friction divided by weight) stays roughly the same for that surface whatever the load; the starting jerk is higher than the sliding force because static friction exceeds kinetic friction.

What changes

What you change: surface, then load in the shoe
What you measure: force on the balance while sliding
What you keep the same: same shoe
steady slow pull
balance held level

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

Friction is the same everywhere.
A bigger shoe has more friction because of its size (the area barely matters; the weight does).
Friction only acts when something is moving.

Safety card

Low riskLearners carry it out

Hazards

spring balance recoil

Controls

pull slowly
do not overload the balance beyond 10 N

Note

Risk assessment before the lesson using Primary RiskAssess or the school's own template.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K-6 Syllabus (2017), current, taught until 2026; code read from the syllabus document on 22 September 2026ST2-9PW-ST ST2-1WS-S
Science and Technology K-6 Syllabus (2024), implemented from 2027; NESA's timeline is 2026 plan and prepare and 2027 start teaching, and schools may choose to implement it during 2026; code read from the outcomes page on 22 September 2026ST2-DAT-01
Australian Curriculum v9AC9S4U03AC9S4I03AC9S4I04

Sources

The pages the author read to write this activity.

All Concept Studio activities