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Physics LG Jan. 30, 2009 Vectors & Projectile Motion Motion is Relative ► Frameof Reference - perspective from which you observe Truck at Rest If the ball is thrown at 60 km/h relative to the truck, at what velocity will the person catch the ball at? Truck Moving Away ► If the ball is thrown at 60 km/h west relative to the truck and the truck moves at 40 km/h east relative to the catcher, at what velocity will the person catch the ball at? Truck Moves Towards ► Ifthe ball is thrown at 60 km/h west relative to the truck and the truck moves at 40 km/h west relative to the catcher, at what velocity will the person catch the ball at? ► Scalar - measurement of magnitude only Ex) mass, volume, speed ► Vector - measurements with both magnitude and direction Ex) velocity, acceleration, force Vectors arrowhead = direction length of arrow = magnitude Vector addition Resultant – sum of vectors Pythagorean Theorem a2 + b2 = c2 ► c2 = a2 + b2 ► c2 = 802 + 602 ► c2 = 6400 + 3600 ► √c2 = √10,000 ► c = 100 km/hr Example Problem ► c2 = a2 + b2 ► c2 = 42 + 32 ► c2 = 16 + 9 ► c2 = 25 ► c = 5 km/h Vector addition ► Pythagorean Theorem - ► Parallelograms - ► Head-to-tail method - ► Trigonometry - Vector Addition http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=51 What is the vertical and horizontal component of a vector? http://www.batesville.k12.in.us/Physics/APPhyNet/Vectors/Hor_&_Vert_Comps.html Projectile Motion Projectile – an object moving through air affected by gravity Projectile Demos ► Shooter/Dropper ► Monkey and Hunter Projectile Motion Horizontal and vertical motion act independently 1 2 d x vt d y at 2 How fast is the ball thrown? ► Vertical ► Horizontal ► d= .5at2 ► v= d/t ► 5 = .5(10)t2 ► v= 20m/1s ► t= 1 second ► v= 20 m/s The ball is thrown at 20 m/s! Upwardly-Moving Projectiles What angle should a ball be kicked to get the farthest? Projectiles launched at the same speed but different angles. Shot Put - 45º is not the ideal angle, why? You are already off the ground 1-2 meters. 45º is the ideal angle for high speed projectiles either. Why? Air resistance must be considered. Fast Moving Projectiles ► What would happen if you threw a ball so fast that the curvature of the earth came into play? Fast Moving Projectiles a projectile traveling fast enough to fall ► Satellite- around the earth rather than into ► To stay in orbit around the earth, a satellite needs to travel at 8 km/s! Hang Time Due Next Week POTW 11s Bull’s eye lab 12s Rocket Lab 30s Motion Worksheet #1 31s Motion Worksheet #2 32s Motion Review Test will be next Thursday Feb 5th ►Study the 1s, 2s, labs, and worksheets ►Use the back page of booklet under motion for note sheet for test.
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