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Review of Quiz 4

Review of Quiz 4. Total: 50 Average: 28.4 High: 47 Low: 5. Problem 1. Problem 1 (5 points): Suppose a 7.5kg mass is rotating about an axis at a distance of 5 m. What is the object’s moment of inertia about the axis? a) 38 kg-m 2 b)190 kg-m 2 c)280 kg-m 2 d)400 kg-m 2 Answer:.

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Review of Quiz 4

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  1. Review of Quiz 4 • Total: 50 • Average: 28.4 • High: 47 • Low: 5 Physics 253

  2. Problem 1 • Problem 1 (5 points): Suppose a 7.5kg mass is rotating about an axis at a distance of 5 m. What is the object’s moment of inertia about the axis? a) 38 kg-m2 b)190 kg-m2 c)280 kg-m2 d)400 kg-m2 • Answer: Physics 253

  3. Problem 2 • Problem 2 (5 points): What is the vector product of AxB if A=3i and B=4j? a) 3i + 4j b) 0 c) 0.7i d) 12k • Answer: Physics 253

  4. Problem 3 • Problem 3 (5 points): A post is driven perpendicularly into the ground and serves as the axis about which a gate rotates. A force of 12N is applied perpendicular to the gate and acts parallel to the ground. How far from the post should the force be applied to produce a torque of 3.0 Nm? a) 0.25m b) 4.0m c) 36m d) 12 m • Answer: Physics 253

  5. Problem 4 • Problem 4 (5 points): A constant torque of 30Nm is applied to a merry-go-round for 10 seconds. Neglecting friction what is the magnitude of the change of the merry-go-round’s angular momentum? a)3kg-m2/s b)0.3kg-m2/s c) 300kg-m2/s d) 3kg-m2/s • Answer: Physics 253

  6. Problem 5 • Problem 5 (5 points): A disk of 4.0 kg and 0.20 m is rotating about its axis of symmetry at w =10 rads/sec. What is the rotational kinetic energy? • Answer Physics 253

  7. Problem 6 • Problem 6 (10 points): Starting from rest a 5.0kg cylinder of radius 0.5m rolls down an inclined plane without slipping or sliding. How much will the height of the cylinder have decreased when the velocity is 10m/s? +5pts Physics 253

  8. +5pts Physics 253

  9. Problem 7 Problem 7(15points): As shown in the figure, a diver of weight 530 N is poised at the right end of a diving board. The board has length 3.90 m. The board has negligible weight and is bolted down at the left end while supported 1.4 m away by a fulcrum. Draw the equilibrium diagram with all three forces involved. Find the forces F1 and F2 that the bolt and fulcrum exert on the board. +5pts Physics 253

  10. +5pts +5pts Physics 253

  11. A Narrative: Where We’ve Been • Started by describing linear motion with constant acceleration, free fall, and projectile motion. • Studied Newton’s 2nd Laws and Law of Gravitation and saw how these can be quantitatively applied to many systems. • Laws naturally lead to concepts of work, energy, and conservation of energy and momentum. • Finally applied these to find complete analog to rotational motion. • We can now describe the mechanical universe over an immense range of distances: a top, a hurricane, and a galaxy. A true achievement and always fun! • Next semester you’ll carry these tools into electromagnetism, in particular vector operations, energy conservation, and potential fields. Physics 253

  12. Comprehensive Multiple Choice Eight questions Five points each Problems Six Questions Points: Two Five point questions Two Ten point questions Two Fifteen point questions Partial Credit Given! Open Book You may bring my notes as well, (but that seems like needlessly killing trees.) Calculators will be needed All Material Covered: Chapters 1-11 Chapter 12, Sections 1,2,3,4 Chapter 14, Sections 1,2 100 Points Final Physics 253

  13. Computing Grades • Four quizzes - 50 points each – 200 points maximum. • Final exam - 100 points - 100 points maximum. • Unit problem sets - 12 points each, due before quiz – 84 points maximum. • Fourteen laboratories - 15 points each - 210 points maximum. (Note: Each student must get 120 points or more in the laboratory to pass the course, regardless of other scores.) • Extra credit – Each problem worth one point. Final extra credit is equal to the fraction of problems correct times 70 - 70 points maximum. Physics 253

  14. Grade Scale • A : 535 or more points • B : 475 to 534 points • C : 416 to 474 points • D : 357 to 415 points • F : less than 357 points (If necessary may be adjusted for curve) If you want your grade stop by or send me email! Physics 253

  15. Final Exam Topics & Problems • Unit conversion • Motion in two dimensions and projectile motion • Free-body analysis with normal, frictional, and gravitational forces involved. • Definition of non-conservative and conservative forces and examples. • Definition and application of work for linear motion • Conservation of mechanical energy • Elastic force and energy • Gravitational force and conservation of energy Physics 253

  16. Scattering in one dimension • Vector Operations (addition, dot, vector) • Moment of Inertia • A free-body analysis involving forces, torque, and moments of inertia • Qualitative understanding of tops and precession • Calculating the impact of the Coriolis force • A statics problem involving forces and torques Physics 253

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