Exploring Forces

Overview

A force is a push or a pull that can change the speed, direction, or shape of an object. This chapter studies different kinds of forces and their effects on objects.

Key concepts

• A force can be a push or a pull.
• Forces can be contact (muscular, friction) or non-contact (gravity, magnetic, electrostatic).
• A force can change the speed, direction, or shape of an object.
• Friction opposes motion between surfaces in contact.
• Gravity pulls all objects towards the Earth.

Important terms / formulae

• Force: a push or pull, measured in newton (N).
• Friction: force that opposes relative motion.
• Gravity: attractive force of the Earth.
• Net force: the overall force when several forces act together.

Solved example or key process

When two children push a box from opposite sides with equal force, the box does not move because the forces are balanced (net force is zero). If one pushes harder, the box moves towards the weaker side, showing an unbalanced net force causes motion.

Important questions

1. Define force and give two examples.
2. Differentiate between contact and non-contact forces.
3. What are the effects a force can produce?
4. How is friction both useful and harmful?

Quick revision

Force is a push or pull. It can change speed, direction, or shape. Contact forces need touching; non-contact forces like gravity and magnetism act at a distance. Balanced forces cause no motion; unbalanced forces do.