Mechanical impulse. Force and time

22/04/2026

The online mechanical impulse simulations on this page will help you to better understand this important concept of physics, how it is calculated and how it is related to other quantities.

This Thematic Unit is part of our Physics collection

Change in Momentum

Change experienced in a body’s momentum, which is numerically equal to the received impulse.

Contact Time

Duration of the interval during which a force acts on an object to modify its state of motion.

Impact Force

Intense force acting over a very short period of time, characteristic of collisions and crashes.

Impulse

Vector quantity product of the applied force by the time interval of action, measured in N·s.

Impulse-Momentum Theorem

Physical relationship stating that the impulse applied to a body equals the change in its linear momentum.

Linear Momentum

Technical term synonymous with momentum, commonly used in the dynamic analysis of systems.

Momentum

Vector quantity defined as the product of a body’s mass and its velocity, measured in kg·m/s.

What is the mechanical impulse

Mechanical impulse is a physical quantity that is defined as the product of the force acting on an object and the time during which the force acts. Mathematically, impulse is expressed as J = F ∆t, where J is the impulse, F is the force and ∆t is the time during which the force acts.

Impulse is a very important quantity in physics, since it is related to many other physical quantities, such as velocity, momentum and kinetic energy.

Units of the mechanical impulse

Mechanical impulse is a vector quantity, which means that it has a direction and a quantity. The direction of the impulse is the same as the direction of the force acting on the object. It has units of Newton-second (N-s) in the International System of Units (SI). It can also be expressed in units of kilogram-meter per second (kg-m/s) in the System of Technical Units (SUT).

Law of conservation of mechanical impulse

The law of conservation of impulse states that, in an isolated system, the total amount of impulse before and after a collision is the same. This means that if two objects collide, the sum of their impulses before the collision is equal to the sum of their impulses after the collision.

Change in Momentum

Change experienced in a body’s momentum, which is numerically equal to the received impulse.

Contact Time

Duration of the interval during which a force acts on an object to modify its state of motion.

Impact Force

Intense force acting over a very short period of time, characteristic of collisions and crashes.

Impulse

Vector quantity product of the applied force by the time interval of action, measured in N·s.

Impulse-Momentum Theorem

Physical relationship stating that the impulse applied to a body equals the change in its linear momentum.

Linear Momentum

Technical term synonymous with momentum, commonly used in the dynamic analysis of systems.

Momentum

Vector quantity defined as the product of a body’s mass and its velocity, measured in kg·m/s.

Explore the exciting STEM world with our free, online, simulations and accompanying companion courses! With them you’ll be able to experience and learn hands-on. Take this opportunity to immerse yourself in virtual experiences while advancing your education – awaken your scientific curiosity and discover all that the STEM world has to offer!

Mechanical impulse simulations

Impulse

Impulse laboratory

Impact
Velocity
Impulse

Impact force and collision time

To inject a given momentum into an object by impact, the force required is inversely proportional to the time of application.

Velocity maximization

In this simulation, the force applied by the machine is constant. To maximize the velocity, the contact time must be increased by dragging the ball to the left. What does the area of the graph below represent?

Impulse laboratory

Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

Augustin-Louis Cauchy

1789

–

1857

Augustin-Louis Cauchy formalized mathematical analysis, providing rigor to calculus and function theory, influencing mathematical physics

“Rigor in mathematics is the key to understanding physical phenomena”

Daniel Bernoulli

1700

–

1782

Daniel Bernoulli formulated Bernoulli’s principle and developed fundamental theories in fluid mechanics and gas dynamics

“Nature is always economical in its means”

Become a giant

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Mechanics, Part 2

Free mode

Mechanics, Part 1

Free mode

Dynamics and Control

Free mode

AP® Physics 2: Challenging Concepts

Free mode

AP® Physics 1 – Part 1: Linear Motion

Free mode

AP® Physics 1

Free mode

AP® Physics 1 – Part 4: Exam Prep

Professional development for Educators

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Teaching with Physical Computing: Soft skills, teamwork and the wider curriculum

Free mode

HP AI Teacher Academy

Free mode

Teach computing: Physical computing with Raspberry Pi and Python

Free mode

Interdisciplinary Teaching with Museum Objects

Giants of science

“If I have seen further, it is by standing on the shoulders of giants”

Isaac Newton

Johannes Kepler

1571

–

1630

Kepler formulated the three laws of planetary motion, establishing elliptical orbits and the relationship between planetary period and distance from the Sun

“The heavens teach the geometry that nature follows”

René Descartes

1596

–

1650

René Descartes developed analytic geometry and contributed to classical mechanics and the study of optics

“Pienso, luego existo”

Become a giant

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Mechanics, Part 2

Free mode

Mechanics, Part 1

Free mode

Dynamics and Control

Free mode

The Basics of Transport Phenomena

Free mode

AP® Physics 1: Challenging Concepts

Free mode

AP® Physics 1 – Part 4: Exam Prep

Free mode

AP® Physics 2: Challenging Concepts

Professional development for Educators

Your path to becoming a giant of knowledge begins with these top free courses

Free mode

Higher education teaching in the age of AI

Free mode

Teaching with Physical Computing: Assessment of Project-Based Learning

Free mode

HP Digital Skills for Educators – Google Workspace

Free mode

Teach teens computing: Impact of technology

Test your knowledge

How is impulse defined in physics, and why is it a key quantity for describing short‑duration interactions?

n physics, impulse is defined as the product of a force applied to an object and the time interval during which that force acts. This makes impulse especially valuable for analyzing situations where forces are very large but act over extremely short periods of time, such as collisions, impacts, or sudden pushes. Instead of tracking how the force changes at every instant—which can be complex and sometimes impossible—impulse provides a global measure of the interaction’s effect. Because impulse directly determines how much the object’s momentum changes, it becomes a central tool for understanding how an object’s motion is altered after a brief but intense interaction.

What is the relationship between impulse and momentum, and how does this connection help analyze collisions and impacts?

Impulse is equal to the change in an object’s momentum. This means that if we know the force applied and the duration of the interaction, we can determine how the object’s velocity changes. This relationship is essential in collision analysis, where forces are large but act for very short times. Instead of needing the exact force at every moment, we can use impulse to understand how momentum is redistributed between the objects involved. This connection allows us to predict post‑collision motion, evaluate energy transfer, and determine whether momentum is conserved in the system.

Why can a quick hit change an object’s motion so much? Does it really make sense that such a short interaction has such a big effect?

Yes, it makes perfect sense. Even though the time is very short, the force during an impact is usually extremely large. Impulse combines both factors—force and time—so a brief but powerful hit can produce a significant change in the object’s momentum. That’s why a fast strike can send a ball flying even if the contact lasts only a fraction of a second.

What happens if I apply a small force for a long time? How come that can also create a large impulse?

Impulse depends on the product of force and time. A small force acting over a long interval can accumulate into a large impulse, producing a noticeable change in momentum. For example, gently pushing an object for several seconds can gradually accelerate it, even though the force itself is weak. The long duration compensates for the small magnitude.

Does it make sense that impulse explains why a strong hit hurts more than a gentle one?

Absolutely. A strong hit involves a much larger force acting over a short time, which produces a large impulse and therefore a sudden, intense change in momentum in the impacted area. That rapid deformation of tissues is what causes pain. A gentle hit produces a much smaller impulse, so the change is less abrupt and the sensation is mild.

To learn and experience

Take your knowledge to the next level with science kits and hands-on tools that connect theory with experimentation

Projectile launcher

Projectile launcher for laboratory studies

Teachers essentials

Notion

Organize your notes, tasks, and projects in one place. Notion combines notes, lists, and calendars in one flexible space.

Canva

Design presentations, diagrams, and infographics with easy-to-use templates and professional results

Genially

Create interactive content, presentations, and educational games in a simple and visual way

Desmos

The most intuitive graphing calculator to explore mathematics and create dynamic classroom activities

Tinkercad

Design in 3D and simulate electronic circuits for free; it’s the perfect tool for simple robotics projects

Get your imagination going

Stories brought to life by captivating voices.

Your Infinite Library

Enjoy the freedom to explore millions of titles and a curated selection of magazines on any device

Join Prime for students and young adults

The best series. Millions of songs. All included with your subscription.

Science made fun

Science museums

Planetariums

Astronomic tours

Nature adventures

Botanical gardens

Zoos

Aquariums

Learn with the best courses

edX

Online courses from leading universities and companies. Learn practical skills and earn professional certifications

Coursera

Courses from leading universities and companies. Learn practical skills and earn professional certifications

Udemy

Thousands of online courses tailored to your level. Learn at your own pace with expert instructors

Mechanical impulse. Force and time

STEM OnLine mini dictionary

Change in Momentum

Contact Time

Impact Force

Impulse

Impulse-Momentum Theorem

Linear Momentum

Momentum

What is the mechanical impulse

Units of the mechanical impulse

Law of conservation of mechanical impulse

STEM OnLine mini dictionary

Change in Momentum

Contact Time

Impact Force

Impulse

Impulse-Momentum Theorem

Linear Momentum

Momentum

Mechanical impulse simulations

Impulse laboratory

Impact force and collision time

Velocity maximization

Impulse laboratory

Giants of science

Augustin-Louis Cauchy

Daniel Bernoulli

Become a giant

Mechanics, Part 2

Mechanics, Part 1

Dynamics and Control

AP® Physics 2: Challenging Concepts

AP® Physics 1 – Part 1: Linear Motion

AP® Physics 1

AP® Physics 1 – Part 4: Exam Prep

Professional development for Educators

Teaching with Physical Computing: Soft skills, teamwork and the wider curriculum

HP AI Teacher Academy

Teach computing: Physical computing with Raspberry Pi and Python

Interdisciplinary Teaching with Museum Objects

Giants of science

Johannes Kepler

René Descartes

Become a giant

Mechanics, Part 2

Mechanics, Part 1

Dynamics and Control

The Basics of Transport Phenomena

AP® Physics 1: Challenging Concepts

AP® Physics 1 – Part 4: Exam Prep

AP® Physics 2: Challenging Concepts

Professional development for Educators

Higher education teaching in the age of AI

Teaching with Physical Computing: Assessment of Project-Based Learning

HP Digital Skills for Educators – Google Workspace

Teach teens computing: Impact of technology

Test your knowledge

How is impulse defined in physics, and why is it a key quantity for describing short‑duration interactions?

What is the relationship between impulse and momentum, and how does this connection help analyze collisions and impacts?

Why can a quick hit change an object’s motion so much? Does it really make sense that such a short interaction has such a big effect?

What happens if I apply a small force for a long time? How come that can also create a large impulse?

Does it make sense that impulse explains why a strong hit hurts more than a gentle one?

You may also be interested

Tools

Scientific calculator

Scientific Dictionary

2026 Best Online STEM Education Platform

Last simulations

To learn and experience

Projectile launcher

Teachers essentials

Notion

Canva

Genially

Desmos

Tinkercad

Science made fun

Science museums

Planetariums