Momentum

Outcomes You will define momentum as a vector quantity equal to the product of the mass and the velocity of an object

Newton’s 1st Law of Motion “A body continues in its state of rest or uniform motion in a straight line unless acted upon by an external unbalanced (net) force”. The unbalanced (or net force) on an object is the sum of all of the forces acting on the object. E.g. 1. Forces of 7.0N east and 5.0N south act on an object. Calculate the net force on the object. E.g. 2. Forces of 10.0N north, 15.0N south, 7.00N east and 18.0N west act on an object. Calculate the net force on the object.

Law of Inertia & Momentum Newton’s 1st Law of Motion is also known as the Law of Inertia Inertia is an objects ability to resist changes in motion based on it’s mass. The idea of inertia is also known as momentum, which can be determined mathematically.

Momentum Momentum is defined as the product of an object’s mass and velocity. We can also relate the idea of momentum to Newton’s Second Law of Motion. How?

Sample Problems 1.0x10³ kg m/s [E] Ex. #1 A mass of 50 kg is moved due east at 20 m/s. Calculate its momentum. 1.0x10³ kg m/s [E] Ex. #2 A baseball is thrown at 20 m/s and is hit back at 30 m/s. Calculate its change in momentum if the ball has a mass of 0.50 kg. -25kg m/s

HOMEWORK CONCEPT/ Textbook QUESTIONS p. 453 #1-3, 6, 15 & 16 CALCULATION QUESTIONS p. 1 #1-7

Impulse

Outcomes You will explain, quantitatively, the concepts of impulse and change in momentum, using Newton’s laws of motion You will explain that technological problems often require multiple solutions that involve different designs, materials and processes and that have both intended and unintended consequences investigate the role of impulse and momentum in the design and function of rockets and thrust systems assess the roles that conservation laws, the concepts of impulse and inertia and Newton’s laws play in the design and use of injury-prevention devices in vehicles and Sports describe the limitations of applying the results from studies of isolated systems in solving a practical problem, as occurred with the early design and deployment of airbags.

Impulse Impulse is defined as the product of the net force and the time the force acts. Impulse = FΔt Newton’s 2nd Law of Motion: a net force will accelerate an object

Impulse-Momentum Theorem A force applied over a time causes a change in momentum of the object. So, impulse and momentum can be equated… Impulse is measured in N s OR kg m/s

How Rockets Work https://www.youtube.com/watch?v=C1TuxJRszVo

Discussion Explain how the principals of momentum and impulse are used in the following: Follow through during swing Advanced materials for clubs, hockey sticks Cushioning in running shoes Padding in helmets Air bags in cars (tested independent of entire car; other factors involved in crash that affected airbag performance)

Car Safety http://www.youtube.com/watch?v=yUpiV2I_IRI The following are all designed to increase the time interval required to stop a motorist during a crash Vehicle crumpling Steering column collapses Airbag leaks after inflating Airbag also distributes force over a larger surface area

Sample Problems Ex. #1 A net force of 12.0 N north acts on an object for 2.00x10-3 s. Calculate the impulse. 2.40x10¯²N s [N] Ex. #2 A net force of 14.0 N acts south on a 6.00 kg object for 1.00 x 10-1 s. What is the change in velocity of the object? 0.233m/s [S]

Force-Time graphs to calculate Impulse Area under the curve!!!

HOMEWORK CONCEPT QUESTIONS p. 467 #1-7 CALCULATION QUESTIONS p. 2 #8-20