Physics131_L07WI10(2)

# Physics131_L07WI10(2) - Physics 131 - Mechanics Le cture7...

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Physics 131 - Mechanics Lecture 7 one dimensional Motion January 22, 2010 Homeyra Sadaghiani

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Oct 24, 2010 Physics 131 - Lecture 7 Announcements HW#3 is due at 9 a.m. on Wed, January 27 th We will check your clicker registrations today. 2
Week Date L# Lecture topic Text reading HW 1 4-Jan 1 Description of course structure, SI units 6-Jan 2 Motion, position, velocity, acceleration 1.1-8 (26 P) HW#0 8-Jan 3 One-dimensional motion 2.1-3 (14 P) 2 11-Jan F1 Furlough (Constant acceleration -Tutorial)   13-Jan 4 Vectors 3.1-4 (13 P) HW#1   15-Jan 5 Constant acceleration 2.4-7 (14 P)   3 18-Jan H1 Holiday (Martin Luther King's Birthday)   20-Jan 6 Two- dimensional motion 4.1-3 (12 P) HW#2   22-Jan 7 Circular and relative motion 4 25-Jan 8 Force, mass, inertial frames HW#3 29-Jan E1 EXAM 1- Chapters 1-4 Oct 24, 2010 Physics 131 - Lecture 7 Lecture Schedule We are here! 3

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Oct 24, 2010 Physics 131 - Lecture 7 Projectile Trajectory 2 0 1 2 0 2 2 0 0 0 0 0 ; ( ) 2 y y x x x x x v x x x g t y x v g x x v v v v v = = - = - ( 29 2 0 2 2 0 0 ( ) tan 2 cos g y x x x v q q æ ö = - ç ÷ è ø This is the equation for a parabola . 0 0 ( ) ; x x t x v t = + 1 2 0 0 2 ( ) y y t y v t gt = + - x 0 = y 0 = 0 4
Oct 24, 2010 Physics 131 - Lecture 7 Path of Projectile ( 29 2 0 2 2 0 0 ( ) tan 2 cos g y x x x v q q æ ö = - ç ÷ è ø http://www.ngsir.netfirms.c 5

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Oct 24, 2010 Physics 131 - Lecture 7 A delighted physics graduate throws her cap into the air with an initial velocity of 24.5 m/s at a 36.9 o angle with the horizontal. The cap is later caught by another student. (Neglect air resistance). (a) Find the total time the cap is in the air. (b) Find the total horizontal distance traveled. Example: A Cap in the Air (0,t 1 =0) (0,t 2 ) 6
Oct 24, 2010 Physics 131 - Lecture 7 A delighted physics graduate throws her cap into the air with an initial velocity of 24.5 m/s at a 36.9 o angle with the horizontal. The cap is later caught by another student. (Neglect air resistance). (a) Find the total time the cap is in the air. (b) Find the total horizontal distance traveled. Example: A Cap in the Air 1 2 0 2 ( ) y y t v t gt = - 1 0 1 2 0 2 When 0, ( ) 0, so t =0 and t =2 / y y y t v gt v g = - = 0 0 0 sin y v v θ = 2 2 0 0 =2 sin / 2(24.5 m/s)(sin36.9 ) /(9.81 m/s ) 3.00 s t v g = ° = (0,t 1 =0) (0,t 2 ) 0 2 0 0 2 cos (24.5 m/s)(cos36.9 )(3.00 s) 58.8 s x x v t v t = = = ° = m 7

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Oct 24, 2010 Physics 131 - Lecture 7 Horizontal Range of a Projectile 1 2 0 2 0 ; 0 y v T gT T = - 1 0 2 0 y v gT - = 0 0 0 2 2 sin y v v T g g θ = = ( 29 2 0 0 0 0 0 0 0 0 2 cos sin 2sin cos x v v R v T v g g q q q q æ ö = = = ç ÷ è ø 0 0 0 cos sin 2 = 2 0 0 sin 2 v R g = R is maximum when θ o =45 o . 8
Oct 24, 2010 Physics 131 - Lecture 7 Simulations on Projectile http://phet.colorado.edu/new/simulations/si 9

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Oct 24, 2010 Physics 131 - Lecture 7 A baseball is hit so that it leaves the bat making a 30 0 angle with the ground. It crosses a low fence at the boundary of the ballpark 100 m from home plate at the same height that it was struck. (Neglect air resistance.) What was its velocity as it left the bat?
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## Physics131_L07WI10(2) - Physics 131 - Mechanics Le cture7...

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