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Unformatted text preview: Study Guide for PHY211 Exam 3 Projectile motion: a projectile will undergo some displacement in the ydirection, where the acceleration is a y = g (up and down) in the exact same time as it takes to move along the x direction to the final x coordinate. If an object is launched with an initial speed of 20 m/s at an angle of 25&, please do not use 20 m/s in any of the kinematics equations. You must break this up into the x and y components!!! Conservation of Momentum: this is really Newton&s 3 rd Law written in a different way. Problem #4 from the 2 nd exam clearly illustrates this point. I asked you to solve the problem using Newton&s Laws i.e. F net =ma, but it&s much simpler to use conservation of momentum. Whenever there is a collision, you should automatically think, p i = p f . Inelastic and elastic collisions: Momentum is conserved in ANY collision UNLESS there is some external force acting on the system. Make sure to choose your system accordingly! If objects stick, the collision is force acting on the system....
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 Spring '10
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