Slip and slide: which material slides furthest

The idea

The material on the underside of an object changes how easily it starts to slide and how far it goes, because some materials grip a surface more than others.

What you need

• A 0.50 m smooth ramp (laminated shelf or plastic tray) that can be tilted on a stack of books
• Four identical wooden cubes about 5 cm across: one left plain, one with sandpaper glued underneath, one with a felt pad underneath and one with a smooth plastic lid glued underneath
• A floor strip of masking tape marked every 5 cm from the bottom of the ramp
• A protractor card or a book stack marked with the number of books used

How to do it

1. Set the ramp on three books. Put the plain wooden cube at the top and let go without pushing. Does it slide or stay put.
2. Add one book at a time until the cube starts to slide on its own. Record the number of books when it first moves.
3. Add one more book so the plain cube slides easily, and keep that ramp height for every slider. Release each slider three times from the top line and read how far it travels along the floor tape; a slider that stays on the ramp scores 0.
4. Record the three distances for each slider and circle the middle one.
5. Put the sliders in order from furthest to shortest and say which underside grips the most.

What you should see

At a low tilt the cube stays put; it starts to slide only when the ramp is steep enough. For wood on wood HyperPhysics gives a static coefficient of 0.4 from the author's own wooden surfaces, so a wooden cube on a wooden ramp first slides at about 22 degrees (arctan 0.4 = 21.8 degrees); on a laminated ramp the angle is different and is what the class measures. In the friction model the static coefficient sets how steep the ramp must be before a slider starts, and the kinetic coefficient sets how quickly it stops on the floor; an underside can be hard to start and still slide well once moving, so the order along the floor shows how much each underside grips while sliding, and which underside grips most (sandpaper, felt, plain wood or plastic) is found by the test, not assumed. For wood on wood (kinetic coefficient 0.3) on a 30 degree, 0.50 m ramp the model gives 1.53 m/s at the bottom; turning the corner onto the floor keeps only the part of that speed along the floor, 1.33 m/s (1.53 times cos 30 degrees), so the cube slides at most about 0.30 m along a wooden floor, and less if it catches its front edge or tips at the corner. The learner knows it worked when each slider's three trials land within a few marks of each other, so the order is clear.

What changes

What you change

material on the underside of the slider

What you measure

distance slid along the floor (cm); tilt at which sliding starts (books)

What you keep the same

• slider size and mass
• ramp height
• release without a push
• floor surface
• three trials each

Common misconceptions

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

• Heavier things slide further (with the same underside, stopping distance does not depend on mass).
• A smooth ramp means everything slides at any tilt.

Safety card

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), NESA. Current syllabus; NESA's timeline is 2026 plan and prepare, 2027 start teaching the 2024 syllabus. Code read from the official syllabus document on 2026-09-22.STe-5PW-STSTe-4MW-STSTe-1WS-S
• Science and Technology K-6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.STE-SCI-01STE-PQU-01
• Australian Curriculum v9AC9SFU02AC9SFU03AC9SFI01AC9SFI02AC9SFI03AC9SFI04

Sources

The pages the author read to write this activity.

1. www.scootle.edu.au/ec/search?accContentId=AC9SFU02
2. www.nsw.gov.au/education-and-training/nesa/curriculum/science/science-and-technology-k-6-2017
3. primaryconnections.org.au/teaching-sequences/foundation/make-it-move
4. hyperphysics.gsu.edu/hbase/frict.html
5. hyperphysics.gsu.edu/hbase/frict2.html