Forces and Motion: The Basics

• New lesson editor
• Biology
• Lower Secondary (Key Stage 3)

Learning Objective

At the end of the lesson you will be able to explain what a force is, recognise types of forces, and apply Newton's Laws of Motion to everyday situations.

What do you already know about forces and how they affect objects?

What is a Force?

A force is a push or pull acting on an object. It can start movement, stop movement, speed things up, slow them down, or change their direction.

Measuring Forces

Forces are measured in Newtons (N), named after Isaac Newton. We use tools like spring balances to measure force.

Balanced vs Unbalanced Forces

Forces are not equal. Object speeds up, slows down, or changes direction.

Unbalanced Forces

Equal and opposite forces act. Object stays at rest or moves at constant speed.

Balanced Forces

Newton's First Law (Inertia)

Objects stay still or keep moving until an unbalanced force acts on them.

Newton's Second Law

Force = Mass × Acceleration (F = ma). More force means more acceleration. Larger mass means less acceleration for the same force.

Newton's Third Law

For every action, there is an equal and opposite reaction. When you jump, you push down on the ground and the ground pushes up on you.

Weight and Mass

Weight

Amount of matter; measured in kilograms (kg); stays the same everywhere.

Force of gravity on an object; measured in Newtons (N); weight changes depending on gravity and is calculated by W = mg.

Mass

Friction

Friction slows things down. It helps us walk and stop cars, but it can cause wear and waste energy. We can reduce friction using lubrication or smoother surfaces.

Pressure

Pressure measures how much force is applied to a certain area. Formula: Pressure = Force ÷ Area (P = F/A). E.g., high heels create more pressure than trainers.

Write down 3 things you learned in this lesson.

Write down 2 things you want to know more about.

Ask 1 question about something you haven't quite understood yet.