What is Force?

📚 Key Concepts

🔹 Definition of Force

Force is a push or pull on an object resulting from the object’s interaction with another object. It’s the invisible hand that can make things move, stop, speed up, slow down, change direction, or even change shape.

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Unit of Force: Newton (N)
SI Unit: 1 Newton = Force needed to accelerate 1 kg mass by 1 m/s²

🔹 Essential Characteristics of Force

Key Properties:

  • Force always involves at least two objects interacting
  • Force can act with contact (contact forces) or without contact (non-contact forces)
  • Force is a vector quantity (has both magnitude and direction)
  • Forces always occur in pairs – when one object exerts force on another, the second object exerts an equal and opposite force back

🔹 Effects of Force on Objects

Force can produce the following effects:

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1. Make a stationary object move

  • Pushing a book on a table
  • Kicking a football at rest

2. Stop a moving object

  • Applying brakes to stop a bicycle
  • A fielder stopping a cricket ball

3. Change the speed of a moving object

  • Pressing the accelerator to speed up a car
  • Wind resistance slowing down a moving vehicle

4. Change the direction of motion

  • Hitting a ball with a bat
  • Steering a car around a corner

5. Change the shape or size of an object

  • Squeezing a balloon
  • Stretching a rubber band
  • Rolling dough into chapati