HS7 - Adams, Russell Homework 7 Due: Oct 27 2006, 11:00 pm...

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Adams, Russell – Homework 7 – Due: Oct 27 2006, 11:00 pm – Inst: Opyrchal, H 1 This print-out should have 10 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. The due time is Central time. 001 (part 1 oF 1) 10 points A block oF mass m slides on a horizontal Frictionless table with an initial speed v 0 . It then compresses a spring oF Force constant k and is brought to rest. The acceleration oF gravity is 9 . 8 m / s 2 . v m k m μ = 0 How much is the spring compressed x From its natural length? 1. x = v 0 mg k 2. x = v 0 m k g 3. x = v 2 0 2 m 4. x = v 0 k g m 5. x = v 0 r mg k 6. x = v 0 r m k correct 7. x = v 2 0 2 g 8. x = v 0 s k mg 9. x = v 0 r k m 10. x = v 0 mk g Explanation: Total energy is conserved (no Friction). The spring is compressed by a distance x From its natural length, so 1 2 mv 2 0 = E i = E f = 1 2 k x 2 , or x 2 = m k v 2 0 , thereFore x = v 0 r m k . Anyone who checks to see iF the units are correct should get this problem correct. keywords: 002 (part 1 oF 2) 10 points A bead slides without Friction around a loop- the-loop. The bead is released From a height 11 . 7 m From the bottom oF the loop-the-loop which has a radius 4 m. The acceleration oF gravity is 9 . 8 m / s 2 . 11 . 7 m 4 m A What is its speed at point A ? Correct answer: 8 . 51587 m / s. Explanation: Let : m = 4 g , R = 4 m , and h = 11 . 7 m . ±rom conservation oF energy, we have K i + U i = K f + U f 0 + mg h = mv 2 2 + mg (2 R ) v 2 = 2 g ( h - 2 R ) . ThereFore v = p 2 g ( h - 2 R ) = r 2(9 . 8 m / s 2 ) h 11 . 7 m - 2(4 m) i = 8 . 51587 m / s .
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Adams, Russell – Homework 7 – Due: Oct 27 2006, 11:00 pm – Inst: Opyrchal, H 2 003 (part 2 of 2) 10 points How large is the normal force on it at point A if its mass is 4 g? Correct answer: 0 . 03332 N. Explanation: The centripetal force is equal to the normal force due to the track and gravity, F c = N + mg , so N = m µ v 2 R - mg = (4 g)(0 . 001 kg / g) × (8 . 51587 m / s) 2 4 m - 9 . 8 m / s 2 = 0 . 03332 N . keywords: 004 (part 1 of 1) 10 points A block starts at rest and slides down a fric- tionless track except for a small rough area on a horizontal section of the track (as shown in the Fgure below). Itleavesthetrackhorizontally, ±iesthrough the air, and subsequently strikes the ground. The acceleration of gravity is 9
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This note was uploaded on 04/03/2009 for the course PHYS 111 taught by Professor Moro during the Spring '08 term at NJIT.

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HS7 - Adams, Russell Homework 7 Due: Oct 27 2006, 11:00 pm...

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