Lect10-Phys172s11-(6.1-6.6-Energy_Principle)

Lect10-Phys172s11-(6.1-6.6-Energy_Principle) - Spring 2011...

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Unformatted text preview: Spring 2011 PHYS 172: Modern Mechanics Lecture 10 – The Energy Principle Read 6.1 – 6.6 Exam results: Multiple choice part average: 47.29/70 = 68 % Hand graded part average: (partially graded): 16/30 = 53% Total average (preliminary): 63% Hardest problem: Ferris wheel Mass m spins around center point with constant speed v in outer space . v & m R CLICKER: What is the magnitude of the net force at the lowest point? string A) 0 N B) C) D) E) mg v p R v mg p R + v mg p R- m Hardest problem: Ferris wheel CLICKER: What is the magnitude of the net force at the lowest point? v & R Mass m spins around center point with constant speed v on Earth . A) 0 N B) C) D) E) mg v p R v mg p R + v mg p R- Hardest problem: Ferris wheel Answer distribution A) 8 N 36.6 % B) 0 N 21.4 C) 808 N 22.4 D) 854 N 3.9 E) 792 N 14.8 v p R v mg p R- v mg p R + An 80 kg person sits on a Ferris wheel with radius 10 m that rotates at a constant rate making 1 turn in 62.8 seconds. What is the magnitude of the net force acting on that person when he is at the lowest point of the Ferris wheel? (Assume g = 10 N/kg) Second hardest concept: vectors ALMOST HALF OF THE STUDENTS HAVE SERIOUS PROBLEM UNDERSTANDING VECTORS!!! READ CHAPTERS 1.5-1.7 CAREFULLY , do relevant problems in the textbook and seek HELP if needed Second hardest concept: vectors What is the direction of A D p p p & & ¡- = Δ , the change in the child’s momentum,...
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This note was uploaded on 04/23/2011 for the course PHYS 172 taught by Professor ? during the Spring '08 term at Purdue.

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Lect10-Phys172s11-(6.1-6.6-Energy_Principle) - Spring 2011...

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