1. What is Work in Physics?

In everyday language, “work” means any physical or mental effort. However, in physics, work has a specific meaning:

📌 Definition of Work:

Work is done when a force is applied to an object, and the object moves in the direction of the applied force.

✅ Formula for Work:

$$W=F\times d\times \cos (\theta )$$

Where:

• $W$ = Work (Joules, J)
• $F$ = Force applied (Newtons, N)
• $d$ = Distance moved in the force’s direction (meters, m)
• $\theta$ = Angle between force and direction of motion

📌 Key Conditions for Work to be Done:
1️⃣ A force must be applied.
2️⃣ The object must move.
3️⃣ The movement must be in the direction of the force.

🚫 Examples Where No Work is Done:

• Pushing a wall (it doesn’t move).
• Carrying a bag while walking (force is vertical, motion is horizontal).

2. Types of Work

🔹 Positive Work

• Force and motion are in the same direction.
• Example: Lifting a box upwards (force applied upward, motion is upward).

🔹 Negative Work

• Force and motion are in opposite directions.
• Example: Friction slowing down a moving car.

🔹 Zero Work

• No movement or force is perpendicular to motion.
• Example: Holding a bag without moving.

3. Units of Work

• The SI unit of work is the Joule (J).
• 1 Joule = Work done when 1 Newton of force moves an object 1 meter in the direction of the force.

📌 Example Calculation:
A person pushes a box with 10 N of force, and it moves 5 meters forward.

W=10×5×cos⁡(0∘)W = 10 times 5 times cos(0^circ)W=10×5×cos(0∘) $$W=50J$$

So, the work done is 50 Joules.

4. Real-Life Applications of Work

🛠 Lifting Objects: Work is done when lifting weights at the gym.
🚗 Driving a Car: The engine does work to move the car forward.
🎢 Roller Coasters: Work is done to lift the coaster to the top.

5. Key Takeaways

✔ Work is done when a force causes movement in the same direction.
✔ Work = Force × Distance × cos(θ).
✔ SI unit of work is the Joule (J).
✔ No movement = No work (even if force is applied).