Equilibrium Examples in Physics

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

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 state in which all forces acting on an object balance so that the net force equals zero and there is no acceleration.

All forces cancel out — the object doesn't accelerate, though it may still be moving at constant velocity.

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: Equilibrium means zero acceleration, not necessarily zero motion.

Common stuck point: Objects moving at constant velocity are also in equilibrium.

Worked Examples

Example 1

easy
A 25 \text{ N} lamp hangs from a single vertical cord. What is the tension in the cord?

Solution

  1. 1
    The lamp is in static equilibrium, meaning the net force on it is zero: \sum F = 0.
  2. 2
    Identify the forces: tension T acts upward, weight W = 25 \text{ N} acts downward.
  3. 3
    Set net force to zero and solve: T - W = 0 \implies T = 25 \text{ N}

Answer

T = 25 \text{ N}
An object in equilibrium has zero net force. For a hanging object, the tension in the supporting cord equals the object's weight.

Example 2

hard
A 50 \text{ N} sign hangs from two cables, each making a 30° angle with the horizontal. What is the tension in each cable?

Practice Problems

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

Example 1

medium
An object is in equilibrium under three forces: F_1 = 10 \text{ N} east, F_2 = 10 \text{ N} north. What is the magnitude and direction of the third force F_3?

Example 2

easy
A 40 \text{ N} sign is held at rest by two vertical supports. One support pulls upward with 25 \text{ N}. What upward force must the second support provide for equilibrium?
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Background Knowledge

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

net forceacceleration