Introduction to Forces - KS3 Physics

Key Points

• A force is a push or a pull acting on an object due to interaction with another object.
• Measured in newtons (N).
• Divided into contact forces and non-contact forces.

What is a Force?

• A force is a push or a pull on an object.
• Measured in newtons (N).
• Two main categories of forces: contact and non-contact.
• Effects of force can be seen such as opening a door.

Scalars and Vectors

• Physical quantity: something measurable.
• Types:
  • Scalar Quantity: Only magnitude.
  • Vector Quantity: Magnitude and direction (e.g., force).
• Vector quantities represented by arrows (length shows magnitude).

Contact Forces

• Act between two physically touching objects.
• Examples:
  • Tension: Pulling force by string, rope, or rod.
  • Friction: Acts between two surfaces resisting motion.
  • Air Resistance: Opposes motion through air.
  • Upthrust: Upward force in fluids (liquid or gas).
  • Thrust: Driving force by an engine.
  • Normal Reaction Force: Balancing force acting at right angles to a surface.

Non-contact Forces

• Act between objects that aren't physically touching.
• Examples:
  • Magnetic Force: Experienced in magnetic fields, can attract or repel.
  • Electrostatic Force: Experienced by charged particles, can attract or repel.
  • Gravitational Force: Attracts masses towards each other.

Effects of Forces on Objects

• Can speed up or slow down objects (e.g., race cars).
• Can change objects' direction (e.g., satellites in motion).
• Can deform objects (e.g., squeezing a foam ball).

Measuring Forces

• Use a force meter (newton meter) to measure force size.
• Important to zero the force meter for accurate measurements.

Teaching Resources

• BBC offers resources and explainer films by Professor Brian Cox on forces, speed, and motion.

Ensure to review each section to understand how forces interact with different objects and the various types of forces that exist.