# What is Momentum?

Source

## Newton's Three Laws Of Motion

1. Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. In other words, an object at rest stays at rest until acted upon by a force, an object in motion stays in motion until acted upon by a force
2. The greater the force, the greater the motion. The greater the mass, the greater the motion. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.
3. For every action, there is an equal but opposite reaction.

The world is wide, and I will not waste my life in friction when it could be turned into momentum. — Frances E. Willard

## What Is Momentum?

Fast moving objects — such as a baseball, a bullet fired from a gun, or a moving car— are very hard to stop.

• And according to Newton's First Law, due to an inherent laziness or inertia, objects have a tendency to want to maintain their current velocity.
• Thus, momentum can be described as mass in motion. All matter that is moving has momentum.

An illustration of Newton's third law in which two skaters push against each other. The skater on the left exerts a force F on the skater on the right, and the skater on the right exerts a force −F on the skater on the right. Although the forces are | Source

Momentum is a vector quantity meaning that not only does it have magnitude but it also has direction.

• Momentum is defined as the tendency of an object to keep moving in the same direction. If an object has lots of momentum, it is difficult to change its direction.
• By applying enough force to an object that can move or is already moving, a change in momentum occurs.
• According to Newton's Second Law, applying force to an object will cause it to accelerate or increase its velocity.
• Momentum depends not only on an object's mass and speed, it also depends upon the direction it is travelling.
• Thus, an object's momentum can change if:
1. The object changes speed, moving either faster or slower;
2. The object changes direction.

An object will remain in motion unless it is interfered with. Friction or a collision from another object are two factors which change momentum. Momentum is conserved as long as an outside force does not interfere with the object.

Newton's Third law applies to collisions between objects. When a collision occurs between two objects, the objects experience force equal in magnitude but opposite in direction.

Click thumbnail to view full-size
When billiard balls collide,their hardness results in an elastic collision. | Source
A bouncing ball captured with a stroboscopic flash at 25 images per second. Each impact of the ball is inelastic, meaning that energy dissipates at each bounce. | Source

## Elastic Collisions

In a perfectly elastic collsion, there is no loss of kinetic energy, for example, to heat, friction or sound. The total kinetic energy of the two objects before the collision is equal to the total kinetic energy of the two objects after they collide. Elastic collisions typically occur between rigid, non-sticky objects such as pool balls or the steel balls of a pendulum.

The Law of Conservation of Momentum which states that both momentum and kinetic energy are conserved, applies to elastic collisions when there is no external force present.

## Inelastic Collisions

In an inelastic collision, the total kinetic energy of the two objects before the collsion is less than the total kinetic energy of the two objects after the collision. At the same time, momentum is conserved. This is true because some of the kinetic energy is transformed into other forms of energy such as heat and sound. Inelastic collisions typically occur between non-rigid, sticky objects such as clay.

## Equation For Momentum

Source
Click thumbnail to view full-size
Launch of Jupiter-C/Explorer 1 at Cape Canaveral, Florida on January 31, 1958. | Source
Source

## Applications Of Momentum

• Rockets using expulsion of gases through the rear of the rocket produce forward momentum allowing the rocket to travel upward.
• Momentum is seen in the game of billiards. Ball A is struck by a pool cue and hits ball B. The momentum is transferred from ball A to ball B. The momentum of ball A decreases as its velocity slows, allowing the momentum of ball B to increase as it gains velocity. The total momentum of both billiard balls stays constant.
• A ballistic pendulum is a device for measuring the momentum of a bullet fired from a gun. Although now obsolete it was used for many years and led to advances in the science of ballistics. This pendulum is still found in physics classrooms today because it can easily demonstrate the principles of momentum and energy.
• A cuckoo clock uses weights and a pendulum system to keep time. Weights slowly pull down the chains which move the gears inside the clock. These gears are kept in time by the moving pendulum. WInding regularly, usually once a day, keeps the clock working.

## Resources Used

Andrew Rader Studios. Physics 4 Kids. Momentum Basics. 2012

Science Clarified. Real Life Chemistry vol3- Physics vol 1. Momentum.

The Physics Classroom. The Impulse-Momentum Change Theorum 2012.

WIkipedia. Ballistic Pendulum. June 1, 2012

## More by this Author

• 8

The Morse Telegraph was the most popular and efficient means of communicating information in the mid-19th C. Even now, in times when other means of communication are unavailable it is in use by military and marine...

• 124

Has one of your kids come home with a science project that has you both stumped? The first time this project came home with my eldest son we spent time scratching our heads and having him research the internet. From...

• 3

Biological perspective links the studies of biology and psychology. Physiological changes and genetics are believed to play a large role in the behaviors of humans and other animals. Biological perspective is the...

MG Singh 4 years ago from Singapore

Well written my friend. Such articles are a rarity on hubpages.

Teresa Coppens 4 years ago from Ontario, Canada Author

I am so glad you enjoyed the hub! I appreciate the compliment on my work.

m abdullah javed 2 years ago

Teresa Coppens, nice hub, good info about momentum and its applications. Thank you.

Teresa Coppens 2 years ago from Ontario, Canada Author