Momentum

SQ4R: Momentum Lesson 1 from Momentum & Collision Chapter at the Physics Classroom Survey (No writing) Check out headings, captions, & subtitles Question (What do you know about momentum?) What do you already know about this subject?  Why is this being assigned by the teacher? Read Ask 3 questions & write down unknown terms  Reread passages that are unclear Relate back to your questions & teacher questions after each passage Recite Summarize the reading in your own words (2 sentences max for each section)  Take quotes of important ideas or parts Respond Fill in “Momentum, Impulse, & Momentum Change” Worksheet. Review Review your notes Answer any questions that may have been resolved by reading Define unknown terms Take notes for your SQ4R on a separate sheet and staple to your momentum and collision worksheet

Momentum-”mass in motion” All objects have mass, therefore if an object is in motion it has momentum. How much stuff is moving and how fast the stuff is moving Momentum is dependent on mass and velocity p = m x v Vector quantity Units kg*m/s direction Example: What is the momentum of a 200kg elephant charging east at 5m/s?

Momentum and Impulse Remember acceleration is the result of an unbalanced force Newtons 2nd Law f= m x a or F = m x Δv/t Impulse is the change in momentum F x t = m x Δv , where F x t is the quantity impulse Impulse occurs whenever a force acts upon an object for a certain amount of time resulting in a change in momentum. Impulse=Change in momentum An object with momentum can be stopped if a force is applied against it for some amount of time.

Impulse and Collision In a collision, an object experiences a force for a specific amount of time, which results in a change in momentum. The mass either speeds up or slows down. This means that during a collision an object experiences IMPULSE! Impulse experienced by an object in a collision is equivalent to a change in momentum. F x t = Δp (units= N x s)

Impulse: Importance of Direction Momentum is a vector quantity The direction of impulse relative to the direction of momentum must be taken into consideration. Impulse in the same direction results in an increase of momentum equal to the amount of impulse. Impulse in the same direction results in an decrease of momentum equal to the amount of impulse.

Rebounding Collision A collision involving a change in direction and speed is known as a rebound collision Elastic collisions rebound with the same speed (large change in velocity!)

Impulse-momentum Change Theorem F x t = m x Δv Force and time are inversely related therefore as the time in which the collision occurs increases the force decreases and vice versa. To minimize applied force collision time can be increased (Airbags-extend the time required to stop the momentum of the driver) To maximize force collision time must be decreased (When is this a good thing?)