Free Body Diagram Examples in Physics

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Free Body Diagram.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Physics.

Concept Recap

A simplified diagram that isolates a single object and represents all external forces acting on it as labelled arrows originating from the object's centre of.

A simplified picture that shows every push and pull acting on one isolated object.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Isolate one object and show all external forces acting on it.

Common stuck point: Only draw forces ON the object, not forces the object exerts on others.

Sense of Study hint: When drawing a free-body diagram, first identify the object of interest and draw it as a simple dot or box. Then systematically add every force acting on it: weight (always down), normal force (perpendicular to surface), friction (opposing motion), tension (along the rope), and any applied forces. Finally, label each arrow with its name and magnitude if known.

Worked Examples

Example 1

easy
A 10 \text{ kg} box rests on a flat surface. Draw and label all forces in the free-body diagram. What are their magnitudes? Use g = 9.8 \text{ m/s}^2.

Solution

  1. 1
    Identify all forces acting on the box: weight (gravity) pulling downward and normal force pushing upward.
  2. 2
    Weight: W = mg = 10 \times 9.8 = 98 \text{ N} downward.
  3. 3
    Since the box is in equilibrium, the normal force equals the weight: N = 98 \text{ N} upward.

Answer

W = 98 \text{ N downward}, \quad N = 98 \text{ N upward}
A free-body diagram shows all forces acting on a single object as arrows from the object's center. For a stationary object on a flat surface, the only forces are weight and normal force, which must balance.

Example 2

medium
A 5 \text{ kg} block is pulled across a rough surface (\mu_k = 0.2) by a 30 \text{ N} horizontal force. List all forces in the free-body diagram and find the acceleration. Use g = 9.8 \text{ m/s}^2.

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

medium
A 4 \text{ kg} block slides down a frictionless ramp inclined at 45°. Identify all forces in the free-body diagram and find the acceleration. Use g = 9.8 \text{ m/s}^2.

Example 2

hard
A 6 \text{ kg} block hangs from two ropes: one horizontal (attached to a wall) and one at 60° above the horizontal (attached to the ceiling). Find the tension in each rope. Use g = 9.8 \text{ m/s}^2.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

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