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Announcements Midterm 2 on Wednesday, Oct. 19. Material: Chapters 7-11 Review on Tuesday (outside of class time) I ll post practice tests on Web
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Title: Announcements 1
  • Announcements
  • Midterm 2 on Wednesday, Oct. 19.
  • Material Chapters 7-11
  • Review on Tuesday (outside of class time)
  • Ill post practice tests on Web
  • You are allowed a 3x5 inch cheat card
  • Go through practice exams homework class examples understand concepts demos
  • Time limit for test 50 minutes
  • 2 Conservation of energy (including rotational energy) Again If there are no non-conservative forces Energy is conserved. Rotational kinetic energy must be included in energy considerations! 3 Black board example 11.5 Connected cylinders.
  • Two masses m1 (5 kg) and m2 (10 kg) are hanging from a pulley of mass M (3 kg) and radius R (0.1 m), as shown. There is no slip between the rope and the pulleys.
  • What will happen when the masses are released?
  • Find the velocity of the masses after they have fallen a distance of 0.5 m.
  • What is the angular velocity of the pulley at that moment?
  • 4 Torque f A force F is acting at an angle f on a lever that is rotating around a pivot point. r is the ______________ between F and the pivot point. This __________________ pair results in a torque t on the lever 5 Black board example 11.6 Two mechanics are trying to open a rusty screw on a ship with a big ol wrench. One pulls at the end of the wrench (r 1 m) with a force F 500 N at an angle F1 80 the other pulls at the middle of wrench with the same force and at an angle F2 90 . What is the net torque the two mechanics are applying to the screw? 6 Torque t and angular acceleration a. Newtons __________ law for rotation. Particle of mass m rotating in a circle with radius r. force Fr to keep particle on circular path. force Ft accelerates particle along tangent. Torque acting on particle is ________________ to angular acceleration a 7 Definition of work Work in linear motion Component of force F along displacement s. Angle g between F and s. Work in rotational motion Torque t and angular displacement q. 8 Work and Energy in rotational motion Remember work-kinetic energy theorem for linear motion External work done on an object changes its __________ energy There is an equivalent work-rotational kinetic energy theorem External, rotational work done on an object changes its _______________energy 9 Linear motion with constant linear acceleration, a. Rotational motion with constant rotational acceleration, a. 10 Summary Angular and linear quantities Linear motion Rotational motion Kinetic Energy Kinetic Energy Torque Force Momentum Angular Momentum Work Work 11 Rolling motion Pure rolling There is no ___________ Linear speed of center of mass 12 Rolling motion The _______ __________ of any point on the wheel is the same. The linear speed of any point on the object changes as shown in the diagram!! For one instant (bottom), point P has _______ linear speed. For one instant (top), point P has a linear speed of ____________ 13 Rolling motion of a particle on a wheel (Superposition of ________ and ___________ motion) Rolling Rotation Linear 14 Rolling motion Superposition principle Rolling motion Pure _________ Pure _______ Kinetic energy of rolling motion 15 Chapter 11 Angular Momentum part 1 Reading assignment Chapter 11.4-11.6 Homework (due Monday, Oct. 17, 2005) Problems 30, 41, 42, 44, 48, 53
  • Torque
  • Angular momentum
  • Angular momentum is conserved
  • 16 Torque and the ______________ Thus far Torque Torque is the _____________ between the force vector F and vector r 17 Torque and the vector product Definition of vector product f
  • - The vector product of vectors A and B is the ___________.
  • C is _________________ to A and B
  • The __________________ of is C ABsinf
  • 18 Torque and the vector product f
  • Use the right hand rule to figure out the direction of C.
  • __________ is C (or torque t, angular velocity w, angular momentum L)
  • _____________ finger is A (or radius r)
  • ____________ finger is B (or force F)
  • 19 Torque and the vector product f Rules for the vector product. 1. 2. 3. 4. 5. Magnitude of C ABsinq is equal to area of ______________ made by A and B If A is ______ to B then . Thus, If A is _______ to B then 20 Torque and the vector product f Rules for the vector product (cont). 6. 21 Black board example 12.2 HW 21 A force F (2.00i 3.00j) is applied to an object that is pivoted about a fixed axis aligned along the z-axis. The force is applied at the point r (4.00i 5.00j).
  • What is the torque exerted on the object?
  • What is the magnitude and direction of the torque vector t.
  • What is the angle between the directions of F and r?
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