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# graded homework sheet 3 - PAP111/PHYS1A Claus-Dieter Ohl...

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PAP111/PHYS1A Graded Homework Sheet 3 25 th of November 2010 Claus-Dieter Ohl Three of your homework sheets will be graded. Only sheets handed in on Monday, 2.12.10 , directly after the lecture are graded . If you can’t attend the lecture pass the solution to a student or place it into my mailbox in the general office before the date. Write your name and student number on the top of each page and staple the pages. Workings and explanatory text are necessary to get points. Success! Spinning and rolling 1) A disc spinning with mass M and radius R, angular speed ω i and angular momentum I is lowered onto a rough surface with friction coefficient μ s,1 . a) Use the impulse approximation for the friction force and the toque to calculate the final center of mass velocity once pure rolling motion sets in. b) Calculate the duration till pure rolling sets in and the distance travelled. c) Does a sphere spinning at the same initial angular speed ωi , with the same mass M, and radius R as the cylinder once it is in contact with the rough surface obtain a larger or smaller
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Unformatted text preview: final velocity? How long does it take for a sphere to reach pure rolling motion? d) Once the cylinder has obtained pure rolling motion it reaches a new, perfectly smooth surface with μ s,2 = 0. Explain why or why not the center of mass velocity is affected by the new surface. e) Discuss what would happen if the spinning cylinder would have been initially lowered onto a perfectly smooth surface. (50 marks) Relativistic Archer 2) Oliver, standing at the rear end of a railroad car of length 100m, shoots an arrow toward the front end of the car. He measures the velocity of the arrow as 0.3c. Ashlee, who was standing on the platform, saw all of this as the train passed her with a velocity of 0.75c. Determine the following as observed by Ashlee: a) The length of the car. b) The velocity of the arrow. c) The time taken by an arrow to cover the length of the car. d) The distance covered by the arrow. (50 marks)...
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• Fall '10
• Claus-DieterOhl
• Friction, Mass, pure rolling motion, Ashlee, angular speed ωi

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