Put a block on a ramp and gravity splits in two: a down-slope pull mg sinθ and a press into the surface mg cosθ. Drag the angle, mass and friction sliders and watch the free-body diagram and every force redraw, then release the block to see whether it slides or holds.
The three sliders each control a different part of the picture. The angle slider tilts the ramp and immediately reshapes the force arrows: steepen it and the down-slope arrow mg sinθ lengthens while the perpendicular arrow mg cosθ shrinks. The friction slider adds a wine-coloured arrow up the slope that opposes sliding, and the mass slider scales the whole diagram at once. Every arrow is drawn to scale, so the geometry of the split is something you see rather than take on trust.
The panel turns those arrows into numbers: the weight, the two components, the normal force and the friction, all in newtons, plus the acceleration. The single most instructive move is to drag the mass slider back and forth. Every force reading swells or shrinks with it, yet the acceleration stays perfectly still — because a = g(sinθ − μcosθ) has no mass in it. A boulder and a pebble on the same ramp accelerate identically, and here you can watch that happen. The underlying rule is just Newton's second law applied along the slope.
Friction is where ramp problems usually go wrong, so the simulator makes the two cases explicit. While tanθ stays below the coefficient of friction the readout says static and the block does not move: the friction shown is whatever it takes to balance mg sinθ, not the maximum. Push the angle past that point and the readout flips to sliding, the friction becomes μN, and pressing release sends the block down the ramp. For the friction force on its own, the guide to friction works through the same ideas.
Notice what steepening does to the normal force. Because N = mg cosθ, tilting the ramp lifts weight off the surface, so the normal force — and the friction it can supply — falls away, reaching zero at a vertical wall where the block is simply in free fall. To put exact numbers on any ramp, open the inclined plane calculator, or explore another setup from the full simulation collection.
The angle slider tilts the ramp from flat to vertical, the mass slider sets how heavy the block is, and the friction slider sets the coefficient of friction between block and surface. As you drag any of them, the free-body diagram redraws to scale and the panel updates the weight, the down-slope and perpendicular components, the normal force, the friction and the acceleration.
Because the ramp acceleration is a = g(sinθ - μcosθ), which has no mass in it. A heavier block feels a bigger down-slope pull but needs proportionally more force to speed up, and the two cancel exactly. Slide the mass from light to heavy and every force arrow grows while the acceleration readout stays frozen — that is the single most useful thing the simulator shows.
The normal force is N = mg cosθ, only the part of the weight pressing into the surface. As the ramp steepens, more of the weight points down the slope and less presses into it, so cosθ shrinks and N falls with it. At a vertical 90° ramp cosθ is zero, so the normal force and the friction it allows both vanish.
A block held by friction begins to slide once tanθ exceeds the coefficient of friction, so the critical angle is the arctangent of that coefficient. Below it the simulator reads static and the block stays put; nudge the angle past it and the readout flips to sliding and the block accelerates down. Raising the friction slider pushes that tipping angle higher.
Yes. Gravity is held at g = 9.81 m/s², Earth's surface value, and shown as fixed text rather than a slider, because the lab is about how angle, mass and friction split the forces on a ramp. To explore how a different gravity changes a fall, use the free fall simulator instead.