Physics Chapter 5:

Momentum and Collisions

Learning targets:

~1. I can identify the action and reaction

forces acting in a system

~2. I can diagram and calculate the components

of force and motion

~3. I can calculate and compare the physical property

of momentum between two objects

~4. I can explain the idea of impulse as it reacts

to change in momentum

~5. I can apply the law of conservation to momentum


Momentum~ mass in motion

Impulse ~ change in momentum

Conservation ~ closed system no change

Elastic~ bounce and spring g back into motion

Inelastic ~ objects that collide and stick together and objects are deformed





Elastic collisions:


Inelastic collisions:

m1v1+m2v2=(m1+m2) v

•p=momentum (kg*m/s)

•m=mass (kilograms)

•v=velocity (m/s)

•∆p=impulse (newtons-seconds)

Key concepts

Newton's Third Law:


- A force is a push or pull that acts upon an object as a result of interaction with other objects

- Contact interactions are normal, frictional, tensional and applied forces

~"For Every Action, There is an Equal but Opposite Reaction"

- In every interaction, there are a pair of forces acting on two interacting objects

- The size of the force on the initial object equals the force on the second object

- The direction of the force of the first and second object are opposite of each other

- Forces always come in equal and opposite action and reaction force pairs


~ Momentum

- Mass in motion

- A quantity describing an objects resistance to stopping

- If an object is in motion, it has momentum

- The amount of momentum an object has depends on how much stuff is moving and how fast it's moving

- Impulse is change in momentum

- Impulse momentum Theorem:

  • Large force and small time
  • Small force and long time
Conservation of Momentum:

- Collisions: momentum is conserved, therefore before=after, supporting The Law of Conservation of Momentum

- closed systems: no changes in mass

- Isolated systems: When an external force on a closed system is equal to zero (no applied force from outside)

- No system is truly isolated on earth, so we assume ideal

- Types of Collisions:

- Assume perfect or ideal

- Inelastic- objects collide together and stick, deforming

Ex: Clay being thrown on the ground

- Elastic- objects bounce and spring back into their shape

Ex: Bumper Cars