Conservation of Momentum: What Is It, and Why Should You Care?

football collision conservation of momentum example

Credit: Public Domain

By Andrew Bennett

Conservation of Momentum Definition

The conservation of momentum is enormously useful, particularly for learning about collisions between objects. Mostly used to describe the collisions of two or more objects, this physics principle means that the total momentum does not change in a closed system. In other words, the total value of momentum is constant when there are no external forces acting on a group of objects.

Conservation of Momentum Equation

Typically, we use an equation that comes from a special case of the Impulse-Momentum Theorem:

When the force on the system is zero, the total momentum does not change. So, we can write an equation stating that the initial total momentum is equal to the final total momentum.

This equation can be expanded by including momentum terms for each object. For example, if we have two objects labeled A and B, respectively, we might write this as:

We could also substitute the equation for momentum into each term and get the result:

Using a known value for total momentum, we can then solve for the velocity of an object before or after a collision.

Video: Momentum Conservation Explained

In this video, you will learn more about the momentum conservation equation. Then, you will learn to solve an example problem involving a person jumping off a skateboard.

Additional Momentum Practice Problems

Since momentum is a vector quantity, we could apply this in two or even three dimensions by treating each dimension separately. To learn how to solve problems like that, be sure to check the rest of the momentum playlist. For an example that combines momentum and energy conservation, check out this video. While you're on YouTube, make sure to subscribe to my channel, as well.

Questions?

If you have questions about the information in this post or the accompanying video, please let me know! I'm happy to help.

Comments

3 Easy Science Experiments to Do with Your Kids

By Amber Bennett Strong STEM (science, technology, engineering, and math) skills set kids up to succeed both in school and later in life. Encouraging them to be interested in these subjects is easier than you might think, especially if you start when they're young. Activities that encourage children to be curious and creative will spark a love of learning. Plus, science experiments and other hands-on STEM projects are a fun way to bond with your kids. Here are three easy science experiments that preschoolers and early elementary students will enjoy. 1. Leakproof Plastic Bag A (age 5) doing the leakproof plastic bag experiment. Our preschooler loves to do any experiment that involves water. I can give her a couple of beakers, and she'll happily pour water back and forth between them, especially if I put a few drops of food coloring in each beaker so she can mix the colors. Another great activity that involves water is the leakproof plastic bag. All you need are: Large plastic

Why Do They Do That? The Physics Behind 3 Famous Animal Behaviors

By Amber Bennett Have you ever wondered about the origins of the phrase, "get your ducks in a row"? What about how the "doggy paddle" works or why squirrels are such amazing jumpers? The answers to all of these questions have one thing in common: physics. Keep reading to learn about the science behind these three famous animal behaviors. How Do Squirrels Leap from Branch to Branch? A squirrel leaps through the air. Photo Credit: caroline legg , CC BY 2.0 , via Wikimedia Commons The death-defying acrobatic maneuvers performed by squirrels look a lot like parkour tricks. But how do they know how to land tricky jumps between bendy tree branches that move with the wind? Researchers say it's a combination of learned behavior (practice makes perfect) and inherited adaptations. To see what determines how far a squirrel is willing to jump and how the leaps are timed, researchers set up an obstacle course in an artificial forest. Then, they used peanuts to encoura

How Virtual Currency Mining Is Hurting the Environment - Science in the News

Datacenters used for cryptocurrency mining use a lot of energy. By Amber Bennett Although cryptocurrencies are virtual, they are having a tangible impact on our environment. Research shows that cryptocurrencies actually are worse for the earth than other types of money. So, why is that? Simply put, it's because of the resources needed to run the supercomputers that mine Bitcoin and other virtual currencies. Energy Use The datacenters used for mining use large amounts of electricity. For example, the global Bitcoin network uses more energy than entire countries . In fact, according to the University of Cambridge Bitcoin Electricity Consumption Index , the network's power demand is the same as more than 14 million typical American homes. Most of the energy used in the datacenters comes from fossil fuels instead of renewable resources. Plus, datacenters' high energy use can destabilize the electric grid. Materials Mining Another way that cryptocurrency impacts the environme

Bennett Science Blog

Search This Blog