What it does
A block sits on a ramp. Drag the ramp to tilt it, choose the surfaces, set the block’s mass and give it a push up or down the slope. The page tells you straight away whether the block stays still, slides down or moves up, and draws the forces on it as arrows: gravity straight down, the support (normal force) at right angles to the ramp, friction along the ramp, and your push. Press Let go to watch it slide, and the page says how long it took to reach the end.
It also works out the angle at which the block starts to slide on its own, the push that just holds it, and the push needed to start it moving up the slope.
It follows the school topics on friction and force: friction and its effects, rough and smooth surfaces, balanced and unbalanced forces (Class 8 Science, exploring forces), and static and kinetic friction, the angle of repose and free-body diagrams (Class 11 Physics, laws of motion). For forces on the flat, with pushes and momentum, see newton's laws sandbox; for what happens once it slides with steady acceleration, see equations of motion.
How to use it
- Choose a Level. Class 8 names the forces in words and explains in plain sentences why the block moves or not. Class 11 puts the numbers on the arrows, adds the dashed mg sin θ component, the normal force, the net force and the acceleration, and lets you set your own μs and μk.
- Tilt the ramp with the angle slider, or drag up and down on the picture.
- Pick the surfaces. Each has a static value μs (how strongly it grips at rest) and a kinetic value μk (the drag while sliding). They are made-up round numbers to show the idea.
- Set the push along the slope: positive pushes up the slope, negative pushes down.
- Press Let go. If friction holds it, nothing happens; otherwise it slides to the end of the 4 m ramp.
Worked example
Open the page: a 10 kg block of wood on a wooden ramp (μs 0.5, μk 0.3) at 20°. Gravity pulls it down the slope with 10 × 9.8 × sin 20° = 33.5 N; friction can hold up to 0.5 × 92.1 = 46 N, so it stays still, held by 33.5 N of friction. It would slide on its own above 26.6° (tan θ = 0.5).
Tilt it to 30°. Now the pull is 49 N but friction can only hold 42.4 N, so it slides down. At Class 11 the page shows a = (−49 + 25.46) ÷ 10 = −2.35 m/s² (2.35 m/s² down the slope). Pushing up the slope with 10 N is enough to hold it, and a push of more than 91.4 N starts it moving up.
Tips
- The angle at which a block starts to slide does not depend on its mass: both the pull down the slope and the friction grow with the weight.
- Friction at rest is only as big as it needs to be. It can point up or down the slope, whichever way stops the block moving.
- Sliding friction is usually smaller than the grip at rest, which is why something that just starts to slide speeds up.
FAQ
Why does a steeper slope have less friction? The block presses less hard on a steeper ramp (the normal force is mg cos θ, which shrinks as θ grows), and friction is proportional to how hard the surfaces press together.
Are the μ values real? They are rounded teaching numbers chosen to behave like the named surfaces. Real values depend on how clean, dry and smooth the surfaces are; measure your own with a tilting board.
Is anything stored? No. The questions are made in your browser and nothing is saved or sent.
Where the numbers come from
- Forces on an inclined plane (mg sin θ along, mg cos θ across), static friction up to μs N and kinetic friction μk N, and the angle of repose tan θ = μs: standard school physics found in any textbook. g = 9.8 m/s² (rounded).
- Checked against an independent x-y vector sum of the forces on 500 random cases and against hand-worked examples. The friction coefficients for the surfaces are made-up, rounded teaching values.
Standard scientific values, such as constants, atomic weights and melting points, are facts found in every textbook; we name where ours were checked. If you are an author or publisher and want a value, a credit or a table changed or removed, tell us and we will act quickly.
Last updated 2026-11-09.