(3)+Momentum

PAGE EDITORS: Gabe Lutzky, Mookie Murray, Michael Cruz

__ Momentum: (P) __ -vector -In words: a measure of how difficult it is to stop/change the velocity of an object -“Inertia in motion” -Eqaution: P=mv (momentum is mass x velocity) -Units: Kg*m/s __ Impluse (I) __ -change in momentum ∑F=Fnet= ma Fnet=m(∆v/∆t) x ∆t Fnet∆t=m∆v Fnet∆t= mVf-mVi Fnet∆t= Pf-Pi Fnet∆t=∆P __ Momentum Conservation __ In words: if no net, external force is applied to a given system of objects, then the sum of their momenta must remain constant Equation: 0=Pf-Pi so Pi=Pf

Ex/ You stand on a deck on a frictionless pirate ship. You fire a 500kg cannon which shoots out a 10kg cannonball with a velocity of 40 m/s to the right. With what velocity does the cannon kick back Vc=-( McbVcb)/Mc Vc= -.8 m/s

__ Types of Collisions __  1. Elastic: Kinetic Energy is conserved; objects don’t stick together

 2. Inelastic: Kinetic Energy is not conserved  a.  Inelastic – objects don’t stick together  b.  Totally/Completely Inelastic – objects stick together

Ex/ A 10,000 kg train careens towards a gorge at 25 m/s. Superman, flying in the other direction, flies into the train and brings the train to rest. If his mass is 90kg, how fast must he have been traveling? P1= Pf so, mtvt = msvs Vs= (10,0000 x 25)/ 90 Vs= -2,777 m/s __Kinetic Energy (KE)__: energy an object ahs just due to the fact it is in motion Equation: KE= ½ mv2

Interesting Videos and Links

[] Article: "How to Turn Your Fist into a Block-Breaking Machine" (Discover Magazine)

[]# A Bruce Lee is awesome and fast montage.

[] Want to know the some of the physics of "free running" (similar in nature ot parkour)? Watch this montage video and read the related article by "Popular Science" columnist Adam Weiner, author of the book Don't Try This at Home! The Physics of Hollywood Movies

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