Physics gets much easier once you understand the difference between... Show more
GCSE Physics Revision Guide: Key Physics Topics





Scalars, Vectors and Force Basics
Think of scalars as simple measurements with just size - like your mass (70kg) or temperature (20°C). Vectors are more complex because they need both size and direction, like velocity or force.
Here's the key difference: speed is scalar (just "how fast"), but velocity is vector ("how fast and in which direction"). Same goes for distance (scalar) versus displacement (vector with direction).
Forces are basically pushes or pulls that can change an object's shape, speed, or direction. You've got contact forces (like friction when you slide down a slope) and non-contact forces (like gravity pulling you down even when you're jumping).
Quick Tip: Remember that force is measured in newtons (N), where 1kN = 1,000N and 1MN = 1,000,000N.

Weight, Resultant Forces and Work Done
Your weight isn't the same as your mass - weight is gravity pulling on your mass. The formula is simple: weight = mass × gravitational field strength. Your mass stays the same on Mars, but your weight changes because gravity is different there.
When multiple forces act on an object, you can replace them with one resultant force that has the same effect. Free body diagrams help you visualise all the forces, whilst resolving forces involves breaking them into horizontal and vertical components using triangles or parallelograms.
Work done happens when a force moves something: W = F × s . One joule equals one newton moving something one metre. Crucially, if nothing moves, no work is done - even if you're pushing really hard against a wall!
Remember: Work and energy have the same units (joules) because when work is done, energy gets transferred.

Forces and Elasticity
You need at least two forces to change an object's shape - one force can only change speed or direction. Think about stretching a spring: you pull one end whilst something holds the other end.
Elastic deformation means the object returns to its original shape (like a proper spring). Inelastic deformation means it stays permanently stretched or bent. Hooke's Law gives us F = k × e, where k is the spring constant (how stiff the spring is) and e is the extension.
The elastic potential energy stored in a stretched spring is Ee = ½ke². This energy is only stored during elastic deformation - if you stretch something too far past its limit of proportionality, it won't store energy properly anymore.
Key Point: A large spring constant means the spring is really stiff and hard to stretch - think car suspension versus a slinky toy.

Moments, Levers and Gears
The moment is the turning effect of a force around a pivot point. You can get a bigger turning effect by applying more force or by positioning that force further from the pivot: M = F × d.
The principle of moments is brilliant for understanding balance: when something is in equilibrium, clockwise moments equal anticlockwise moments. This is why you can lift someone heavier than you on a seesaw by sitting further from the middle.
Stability depends on having a wide base and keeping the centre of mass low. Gears work by transferring turning effects - a larger output gear gives more turning force than the input gear, but the force between the gear teeth is always equal and opposite.
Real-world Application: Spanners, scissors, bottle openers and bike gears all use these moment principles to make tasks easier.
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GCSE Physics Revision Guide: Key Physics Topics
Physics gets much easier once you understand the difference between scalars and vectors, and how forces work in the real world. This guide covers everything from basic measurements to complex force calculations, plus some brilliant applications like levers and springs... Show more

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Scalars, Vectors and Force Basics
Think of scalars as simple measurements with just size - like your mass (70kg) or temperature (20°C). Vectors are more complex because they need both size and direction, like velocity or force.
Here's the key difference: speed is scalar (just "how fast"), but velocity is vector ("how fast and in which direction"). Same goes for distance (scalar) versus displacement (vector with direction).
Forces are basically pushes or pulls that can change an object's shape, speed, or direction. You've got contact forces (like friction when you slide down a slope) and non-contact forces (like gravity pulling you down even when you're jumping).
Quick Tip: Remember that force is measured in newtons (N), where 1kN = 1,000N and 1MN = 1,000,000N.

Sign up to see the content. It's free!
- Access to all documents
- Improve your grades
- Join milions of students
Weight, Resultant Forces and Work Done
Your weight isn't the same as your mass - weight is gravity pulling on your mass. The formula is simple: weight = mass × gravitational field strength. Your mass stays the same on Mars, but your weight changes because gravity is different there.
When multiple forces act on an object, you can replace them with one resultant force that has the same effect. Free body diagrams help you visualise all the forces, whilst resolving forces involves breaking them into horizontal and vertical components using triangles or parallelograms.
Work done happens when a force moves something: W = F × s . One joule equals one newton moving something one metre. Crucially, if nothing moves, no work is done - even if you're pushing really hard against a wall!
Remember: Work and energy have the same units (joules) because when work is done, energy gets transferred.

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- Improve your grades
- Join milions of students
Forces and Elasticity
You need at least two forces to change an object's shape - one force can only change speed or direction. Think about stretching a spring: you pull one end whilst something holds the other end.
Elastic deformation means the object returns to its original shape (like a proper spring). Inelastic deformation means it stays permanently stretched or bent. Hooke's Law gives us F = k × e, where k is the spring constant (how stiff the spring is) and e is the extension.
The elastic potential energy stored in a stretched spring is Ee = ½ke². This energy is only stored during elastic deformation - if you stretch something too far past its limit of proportionality, it won't store energy properly anymore.
Key Point: A large spring constant means the spring is really stiff and hard to stretch - think car suspension versus a slinky toy.

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- Access to all documents
- Improve your grades
- Join milions of students
Moments, Levers and Gears
The moment is the turning effect of a force around a pivot point. You can get a bigger turning effect by applying more force or by positioning that force further from the pivot: M = F × d.
The principle of moments is brilliant for understanding balance: when something is in equilibrium, clockwise moments equal anticlockwise moments. This is why you can lift someone heavier than you on a seesaw by sitting further from the middle.
Stability depends on having a wide base and keeping the centre of mass low. Gears work by transferring turning effects - a larger output gear gives more turning force than the input gear, but the force between the gear teeth is always equal and opposite.
Real-world Application: Spanners, scissors, bottle openers and bike gears all use these moment principles to make tasks easier.
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What is the Knowunity AI companion?
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
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