Force

Also known as: push, pull, F

definition

A push or pull interaction between two objects that can cause a change in an object's velocity (speed or direction), described as a vector quantity measured in newtons. Force is the central concept in classical mechanics, governing everything from how bridges hold up to how rockets launch.

💡 Intuition

Anything that makes something move, stop, speed up, slow down, or change direction.

Core Idea

Force is an interaction between objects that changes motion.

Formal View

Force is a vector quantity defined by Newton's second law: \vec{F}_{\text{net}} = m\vec{a}. More generally, \vec{F} = \frac{d\vec{p}}{dt}, the time rate of change of momentum.

🔬 Example

Pushing a shopping cart, gravity pulling you down, a magnet attracting metal.

🎯 Why It Matters

Force is the central concept in classical mechanics, governing everything from how bridges hold up to how rockets launch. Every engineering design and safety calculation begins with force analysis.

⚠️ Common Confusion

Force isn't the same as motion—an object can have forces on it and still not move (if forces balance).

💭 Hint When Stuck

When solving a force problem, first draw a free-body diagram showing all forces on the object. Then resolve each force into components along your chosen axes. Finally, apply Newton's second law (F_{\text{net}} = ma) separately for each axis to find unknown forces or acceleration.

Related Concepts

Prerequisites

acceleration mass

Next Steps

newtons first law newtons second law newtons third law

How Force Connects to Other Ideas

To understand force, you should first be comfortable with acceleration and mass. Once you have a solid grasp of force, you can move on to newtons first law, newtons second law and newtons third law.

Learn More

A Parent's Guide to Concept-First Learning — In-depth guide Introduction to Physics Concepts — In-depth guide

Compare With Similar Concepts

Mass vs Weight

Go Deeper

Worked Examples

Step-by-step solved problems

Practice Problems

Test your understanding

Formula Explained

Notation, derivation, and common mistakes

Frequently Asked Questions

What is Force in Physics?

A push or pull interaction between two objects that can cause a change in an object's velocity (speed or direction), described as a vector quantity measured in newtons.

Why is Force important?

Force is the central concept in classical mechanics, governing everything from how bridges hold up to how rockets launch. Every engineering design and safety calculation begins with force analysis.

What do students usually get wrong about Force?

Force isn't the same as motion—an object can have forces on it and still not move (if forces balance).

What should I learn before Force?

Before studying Force, you should understand: acceleration, mass.

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