Gravity
Spring
Drag
Thrust
Net force
Drag the orange body and release to launch it
Every physics-simulation builder starts the same way: define an object's mass and position, then attach force models to it — gravity, a spring, friction, a thrust — and let Newton's second law turn their sum into motion. This sandbox makes that pipeline visible in a bounded 2D box. A single body is tethered to a fixed anchor by a Hooke's-law spring; you switch gravity, spring stiffness, viscous drag and a constant thrust on and off independently, and each active force is drawn as its own colored arrow rooted at the body while a bold white arrow shows their vector sum. A live bar chart tracks all five magnitudes at once, and you can grab the body directly with the mouse to fling it like a slingshot. Live readouts track the net force magnitude, the resulting acceleration from a = F/m, and the body's current speed as semi-implicit Euler integration steps the trajectory forward frame by frame.