Physics NH Primary Day Review of momentum for Quiz Review Problems

Momentum A quantity of motion found by multiplying an object’s mass by its velocity Is a vector (Magnitude and direction are important)

Units of momentum Kg m/s

Equation of momentum P = m v

Examples of objects with momentum Anything that has mass and is moving

Examples of objects without momentum Anything that has no velocity A bus that is stopped has less momentum than a flea that is moving, but more inertia

Impulse Is the change of momentum Units are the same as momentum

Impulse equation ∆p = F ∆t = m ∆v ∆v = vf - vi

Which parts of the equation = the impulse? Impulse = F ∆t Impulse = m ∆v Impulse = pf - pi

Relationship between force and change in momentum To change the momentum of an object, a net force must be applied to it. Examples: Hockey stick on puck Wall on car Bat on softball

Safety features in cars that protect you during a crash Seat belt Air bags Cushioned dashboard, steering weel Padded headrest Crumple zones

What value do safety features extend? The time of the crash Impulse = Force x time

What value is decreased as a result of those safety features? The amount of force needed to stop the car (and you)

Which car has the greatest impulse? They have the same change in momentum The car hitting a brick wall will have more force applied over a shorter time

Conservation of momentum In a closed, isolated environment, momentum is not created or destroyed only transferred

Closed system Any arrangement of 2 or more objects that do not gain or lose mass The objects interact with each other

Isolated system Any arrangement of 2 or more objects that undergo NO external net force during their interaction

Conservation of Mom(entum) equation For 2 objects (can be expanded) m1v1 + m2v2 = m1v1’ +m2v2’

Answers to review questions #1 4.8 N s #2 42 m/s #3a -100 kg m/s #3b kg m/s # m/s backwards