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Lecture214Week2

# Lecture214Week2 - This Week Gravity Dropping and throwing...

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This Week Gravity: Dropping and throwing objects From Baseballs to satellites What causes motion. All changes involve motion Mass and Weight What’s the difference? Friction good and bad A necessary evil. Extinction of the dinosaurs 12/09/11 Physics 214 Fall 2011 1

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12/09/11 Physics 214 Fall 2011 2 One dimensional motion and gravity When we drop an object it’s velocity continues to increase that means there is an acceleration. Near the earths surface the value of this acceleration is g = 9.8m/s 2. This is due to the attractive force of gravity and g does vary over the earth because the earth is not a perfect sphere and because of the rotation of the earth. On the moon g is much smaller The equations of motion are: v = v 0 + at d = v 0 t + 1/2at 2 v 2 = v 0 2 + 2ad d = ½(v + v 0 )t (starting at d =0) + For this case all quantities are +
12/09/11 Physics 214 Fall 2011 3 Throwing vertically In the example shown a ball is thrown vertically.The acceleration is minus 9.8m/s 2 and the motion is symmetric. v = v 0 + at at t=0 v = v 0 At the top v = 0 and t = v 0 /9.8 At the bottom t = 2v 0 /9.8 and v = - v 0 time up and down = 2 x time to top d = v 0 t + 1/2at 2 so d=0 when t = 0 or t = -2v 0 /a or 2v 0 /9.8 since a = -9.8 v 2 = v 0 2 + 2ad At d = 0 v = +v 0 (t = 0) Or v = -v 0 ( t = 2v 0 /9.8) g = -9.8m/s 2 +

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12/09/11 Physics 214 Fall 2011 4 One dimensional motion and gravity When we drop an object it’s velocity continues to increase that means there is an acceleration. Near the earths surface the value of this acceleration is g = 9.8m/s 2. This is due to the attractive force of gravity and g does vary over the earth because the earth is not a perfect sphere and because of the rotation of the earth. On the moon g is much smaller The equations of motion are: v = v 0 + at d = v 0 t + 1/2at 2 v 2 = v 0 2 + 2ad d = ½(v + v 0 ) (starting at d =0) + For this case all quantities are +
12/09/11 Physics 214 Fall 2011 5 One dimensional motion and gravity When we drop an object it’s velocity continues to increase that means there is an acceleration. Near the earths surface the value of this acceleration is g = 9.8m/s 2. This is due to the attractive force of gravity and g does vary over the earth because the earth is not a perfect sphere and because of the rotation of the earth. On the moon g is much smaller The equations of motion are: v = v 0 + at d = v 0 t + 1/2at 2 v 2 = v 0 2 + 2ad d = ½(v + v 0 ) (starting at d =0) + For this case all quantities are +

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12/09/11 Physics 214 Fall 2011 6 Projectile Motion If we throw an object so that it’s initial velocity is horizontal then ignoring friction it will continue to move with this velocity in the horizontal direction but it will also start to fall so that it’s trajectory will be curved.
12/09/11 Physics 214 Fall 2011 7 Motion in two dimensions If we take two axes at right angles we can analyze the motion along each axis separately and determine properties of the whole motion. We will only deal with cases where there is a constant

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Lecture214Week2 - This Week Gravity Dropping and throwing...

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