📖 Comprehensive Note
A body is said to be in equilibrium when the resultant force acting on it is zero. This means that all the vectors (forces) acting on the body are balanced and cancel one another.
When forces are in equilibrium, they do not cause any change in the motion of the body. The combined effect of all the forces acting together is zero.
📌 Conditions for Equilibrium
For a body to be in equilibrium, the following conditions must be satisfied:
- The sum of all horizontal forces acting on the body must be zero.
- The sum of all vertical forces acting on the body must also be zero.
When these conditions are met, the forces balance completely and equilibrium holds.
📌 Effect of Equilibrium on a Body
A body in equilibrium may either:
- Remain at rest, or
- Move with a constant velocity in a straight line.
This happens because the forces acting on the body cancel each other, resulting in no acceleration. As long as the resultant force remains zero, the state of motion of the body does not change.
- Resultant force = 0
- Horizontal forces balance
- Vertical forces balance
- No acceleration occurs
- Body remains at rest or moves with uniform velocity
🎤 Lyrics
📊 Line-by-Line Study Guide
| Lyric Line | Explanation |
|---|---|
| A body is said to be in equilibrium, | Defines equilibrium as a state where forces acting on a body are balanced. |
| When the resultant force is zero, | Equilibrium occurs when the net (resultant) force acting on the body is zero. |
| All the vectors acting on the body, | Refers to all forces (vectors) applied to the body. |
| Balance together as they go. | The forces cancel each other due to equal magnitude and opposite direction. |
| The sum of horizontal forces is zero, | For equilibrium, forces acting horizontally must balance. |
| The sum of vertical forces is too, | For equilibrium, forces acting vertically must also balance. |
| When these conditions are satisfied, | Indicates that equilibrium depends on meeting both force conditions. |
| Equilibrium holds true. | Confirms that the body is in equilibrium when conditions are met. |
| The body remains at rest completely, | Describes static equilibrium where the body does not move. |
| Or moves with velocity that stays the same, | Describes dynamic equilibrium where the body moves at constant velocity. |
| Because the forces cancel each other, | No acceleration occurs because the net force is zero. |
| And equilibrium is the name. | Concludes by naming the balanced condition as equilibrium. |
💡 Mnemonics
To remember the meaning of Equilibrium, use the mnemonic:
⚖️ ZERO
- Z – Resultant force is Zero
- E – Forces are Equal and opposite
- R – Body remains at Rest
- O – Or moves with constant velocity
To remember the CONDITIONS for equilibrium, use:
↔️ UP–DOWN–BALANCE (UDB)
- U – Upward forces = downward forces (vertical balance)
- D – Rightward forces = leftward forces (horizontal balance)
- B – Body stays balanced (equilibrium holds)
One-Line Exam Recall Sentence:
“When forces balance horizontally and vertically, the resultant is zero, so the body rests or moves uniformly.”
❓ Quiz
1. A body is said to be in equilibrium when:
2. Which condition must be satisfied for equilibrium?
3. A body in equilibrium may:
4. When forces cancel each other, the body:
5. Equilibrium occurs because:
🃏 Flashcards
What is equilibrium of a body?
What is the resultant force in equilibrium?
State the horizontal condition for equilibrium
State the vertical condition for equilibrium
How does a body behave when in equilibrium?
🎯 Drag & Drop: Equilibrium of Vectors
Drag each situation to the correct category.
📌 Summary
- A body is said to be in equilibrium when the resultant (net) force acting on it is zero.
- All the forces (vectors) acting on the body balance each other.
- For equilibrium to occur:
- The sum of horizontal forces must be zero.
- The sum of vertical forces must also be zero.
- When a body is in equilibrium, it either:
- Remains at rest, or
- Moves with constant velocity in a straight line.
- Equilibrium occurs because forces cancel each other, producing no acceleration.
- This concept is important in understanding balance, stability, and motion in physics.