sy17_oct31_07hc - Physics 207: Lecture 17, Pg 1 Physics...

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Unformatted text preview: Physics 207: Lecture 17, Pg 1 Physics 207, Physics 207, Lecture 17, Oct. 31 Lecture 17, Oct. 31 Agenda: Agenda: Review for exam Review for exam Exam will be held in rooms B102 & Exam will be held in rooms B102 & B130 in Van Vleck at 7:15 PM Assignment: Assignment: MP Homework 7, Ch. 11, 5 problems, MP Homework 7, Ch. 11, 5 problems, NOTE: Due Wednesday at 4 PM NOTE: Due Wednesday at 4 PM MP Homework 7A, Ch. 13, 4 problems, available today MP Homework 7A, Ch. 13, 4 problems, available today Physics 207: Lecture 17, Pg 2 Example Example Gravity, Normal Forces etc. Gravity, Normal Forces etc. Consider a women on a swing: When is the tension on the rope largest ? And is it : (A) greater than (B) the same as (C) less than the force due to gravity acting on the woman Physics 207: Lecture 17, Pg 3 Gravity, Normal Forces etc. Gravity, Normal Forces etc. At the bottom of the swings and is it (A) greater than the force due to gravity acting on the woman v m g T F c = m a c = m v 2 / r = T- mg T = mg + m v 2 / r m g T F c = m 2 / r = 0 = T mg cos F T = m aT = mg sin Physics 207: Lecture 17, Pg 4 Newtons Laws Newtons Laws Three blocks are connected on the table as shown. The table has a coefficient of kinetic friction of 0.350, the masses are m 1 = 4.00 kg, m 2 = 1.00kg and m 3 = 2.00kg. a) What is the magnitude and direction of acceleration on the three blocks ? b) What is the tension in the two cords ? m 1 T 1 m 2 m 3 Physics 207: Lecture 17, Pg 5 Problem Problem Three blocks are connected on the table as shown. The table has a coefficient of kinetic friction of K =0.40 , the masses are m 1 = 4.0 kg, m 2 = 1.0 kg and m 3 = 2.0 kg. (A) FBD (except for friction) (B) So what about friction ? m 1 T 1 m 2 m 3 m 2 g N m 3 g m 1 g T 3 T 1 Physics 207: Lecture 17, Pg 6 Problem recast as 1D motion Problem recast as 1D motion Three blocks are connected on the table as shown. The center table has a coefficient of kinetic friction of K =0.40 , the masses are m 1 = 4.0 kg, m 2 = 1.0 kg and m 3 = 2.0 kg. m 1 m 2 m 3 m 2 g N m 3 g m 1 g T 3 T 1 frictionless frictionless m 1 g > m 3 g and m 1 g > ( k m 2 g + m 3 g) and friction opposes motion (starting with v = 0) so f f is to the right and a is to the left (negative) f f Physics 207: Lecture 17, Pg 7 Problem recast as 1D motion Problem recast as 1D motion Three blocks are connected on the table as shown. The center table has a coefficient of kinetic friction of K =0.40 , the masses are m 1 = 4.0 kg, m 2 = 1.0 kg and m 3 = 2.0 kg. m 1 m 2 m 3 m 2 g N m 3 g m 1 g T 3 T 1 frictionless frictionless x-dir: 1. F x = m 2 a = k m 2 g - T 1 + T 3 m 3 a = m 3 g - T 3 m 1 a = - m 1 g + T 1 Add all three: ( m 1 + m 2 + m 3 ) a = k m 2 g + m 3 g m 1 g f f T 3 T 1 Physics 207: Lecture 17, Pg 8 Lecture 17, Lecture 17, Exercise Exercise Work/Energy for Non-Conservative Forces Work/Energy for Non-Conservative Forces A. 2.5 J B. 5.0 J C. 10. J D.-2.5 J E.-5.0 J F.-10. J 1 m e t e...
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sy17_oct31_07hc - Physics 207: Lecture 17, Pg 1 Physics...

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