Physics / core

Net Force

Also known as: resultant force, total force

definition

The single resultant force obtained by vector addition of all individual forces acting on an object, which alone determines the object's acceleration according to Newton's second law. Net force is the single quantity that determines whether an object accelerates, decelerates, or maintains constant velocity.

This concept is covered in depth in our understanding net force and motion, with worked examples, practice problems, and common mistakes.

๐Ÿ’ก Intuition

What you get when you add up all pushes and pulls, accounting for direction.

Core Idea

Only the net force determines acceleration, not individual forces.

Formal View

The net force is the vector sum of all forces acting on a body: \vec{F}_{\text{net}} = \sum_{i} \vec{F}_i. By Newton's second law, \vec{F}_{\text{net}} = m\vec{a}.

๐Ÿ”ฌ Example

Two people push a box: 10\text{N} right + 3\text{N} left = 7\text{N} right (net force).

๐ŸŽฏ Why It Matters

Net force is the single quantity that determines whether an object accelerates, decelerates, or maintains constant velocity. It is the foundation of every force-and-motion problem in physics.

โš ๏ธ Common Confusion

Forces in opposite directions subtract; forces in the same direction add.

๐Ÿ’ญ Hint When Stuck

When you see a net force problem, first draw a free-body diagram and list every force with its direction. Then add forces in the same direction and subtract those in opposite directions. Finally, the net force determines the object's acceleration via F_{\text{net}} = ma.

Related Concepts

Prerequisites

How Net Force Connects to Other Ideas

To understand net force, you should first be comfortable with force and vectors. Once you have a solid grasp of net force, you can move on to equilibrium and free body diagram.

Learn More

Go Deeper

Want the Full Guide?

This concept is explained step by step in our complete guide:

Forces, Motion, and Energy: A Concept Bridge Guide โ†’

Frequently Asked Questions

What is Net Force in Physics?

The single resultant force obtained by vector addition of all individual forces acting on an object, which alone determines the object's acceleration according to Newton's second law.

Why is Net Force important?

Net force is the single quantity that determines whether an object accelerates, decelerates, or maintains constant velocity. It is the foundation of every force-and-motion problem in physics.

What do students usually get wrong about Net Force?

Forces in opposite directions subtract; forces in the same direction add.

What should I learn before Net Force?

Before studying Net Force, you should understand: force, vectors.

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