Draw a free body diagram the way physics is really done — one object, every force on it as an arrow, added up as vectors. Load a classic scenario (a block on the ground, a block on a frictionless incline, a sign hanging from two ropes, a box pushed against friction, an accelerating elevator) or add your own forces, then drag any arrowhead to change its size and direction. A live panel resolves the forces into ΣFx, ΣFy and the resultant, tells you whether the body is in equilibrium, and gives the acceleration from a = Fnet/m. It all runs on your device.
Pick a scenario, then drag any arrowhead — or add your own forces
ΣFx (horizontal)0.0 N
ΣFy (vertical)0.0 N
Net force |Fnet|0.0 N
Direction—
In equilibrium?Yes
Acceleration a = F/m0.00 m/s²
One body, every force, added as vectors. A free body diagram isolates a single object and draws each external force — weight, the normal force, tension, friction, any push or pull — as an arrow. Add the arrows tip-to-tail, or resolve them into ΣFx and ΣFy, and you get the resultant Fnet. If it is zero the body is in equilibrium — at rest or moving at constant velocity; if not, Newton's second law gives it an acceleration a = Fnet/m in the direction of the resultant.
How It Works
Isolate the body, draw every force, then add the arrows as vectors.
1
Isolate the body and its forces
A free body diagram shows one object and nothing else — just the external forces acting on it, each drawn as an arrow from the body in the direction it pushes or pulls, with a length that stands for its size. Load a scenario to see a correct set of forces, or press Add force to place your own. Weight, the normal force, tension, friction and applied pushes each get their own colour.
2
Size and aim each arrow
Drag an arrowhead to change a force's magnitude and direction at once, or select it and use the magnitude and direction sliders for precision. As you do, the tool resolves every force into horizontal and vertical components and adds them, so the numbers update the instant an arrow moves.
3
Read the resultant
The dashed white arrow is the net force — the vector sum of everything else. The panel shows ΣFx, ΣFy, the size and direction of Fnet, whether the body is in equilibrium, and the acceleration a = Fnet/m for the mass you set. Balance the arrows and the resultant vanishes; unbalance them and it points the way the body accelerates.
What is a free body diagram?
A free body diagram is a sketch of a single object with every external force acting on it drawn as an arrow, pointing in the force's direction and scaled to its size. It strips away everything except the object and its forces so you can add them up as vectors. Common forces include weight (gravity), the normal force from a surface, tension in a rope, friction, and any applied push or pull. This maker lets you build one by loading a standard scenario or adding your own arrows, then shows the resultant.
How do you find the net force from a free body diagram?
You add the forces as vectors. Break each force into horizontal and vertical components, add all the horizontal parts to get ΣFx and all the vertical parts to get ΣFy, and the net force is the vector with those components. Its size is √(ΣFx² + ΣFy²) and its direction is the angle of that vector. This tool does the sum live as you change the arrows and draws the resultant as a dashed white arrow.
What does it mean for a body to be in equilibrium?
A body is in equilibrium when the forces on it cancel out, so the net force is zero. By Newton's first law it then has zero acceleration — it stays at rest or keeps moving at constant velocity. On a free body diagram equilibrium means the arrows close up: every direction is balanced. Load the "block on the ground" or "pushed at constant velocity" scenario here and you will see the net force read zero and the equilibrium flag turn to yes.
How is acceleration related to the free body diagram?
By Newton's second law, the acceleration is the net force divided by the mass: a = Fnet/m, pointing the same way as the net force. So once the diagram gives you the resultant, dividing by the object's mass gives its acceleration. This tool shows a = Fnet/m directly from a mass you set, so you can see a block on a frictionless incline accelerate down the slope while a balanced box does not accelerate at all.