# Free-body diagram

A sketch of one object with arrows for every force acting on it. It turns a messy problem into F = ma.

Physics (university) · Part 02: Newton's laws and forces · Card 8 of 10 · Last updated 2026-10-19

## Analogy

A character sheet that lists everything pushing on one object.

## Example

**Steps to draw**

1 Draw object as a dot.
2 Add each force arrow.
3 Pick x and y axes.
4 Write F = ma each way.

## In practice

Draw the box alone, then add weight, normal force, push and friction as arrows.

## Practice

### Flashcards

- **What do you draw first in a free-body diagram?** The object alone, as a dot or box, with all force arrows on it.

### Interview questions

**A 10 kg block slides down a 30 degree ramp with friction coefficient 0.2. Find its acceleration.**

- Draw a free-body diagram
- Weight component along slope is mg sin theta
- Friction is coefficient times mg cos theta
- Net force over mass gives acceleration

## Questions people ask

### What should I include in a free-body diagram?

Include only the forces acting on the chosen object, such as weight, normal force, tension, friction and applied pushes. Do not draw forces that the object exerts on others, and do not draw acceleration as a force. Label each arrow and pick axes before writing equations.

### How do I pick axes for a slope problem?

Tilt the axes so one runs along the slope and one runs perpendicular to it. Then only weight needs splitting into components, and the acceleration lies along one axis. This makes the equations much simpler than using flat horizontal and vertical axes.

## Related concepts

- [Friction](https://studyvisually.com/learn/science/physics-university/physics-university-part-2/physics-university-part-2-concept-7)
- [Inclined plane](https://studyvisually.com/learn/science/physics-university/physics-university-part-2/physics-university-part-2-concept-10)
- [Newton's first law](https://studyvisually.com/learn/science/physics-university/physics-university-part-2/physics-university-part-2-concept-1)
- [Net force](https://studyvisually.com/learn/science/physics-university/physics-university-part-2/physics-university-part-2-concept-2)

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