{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Homework 25

Homework 25 - sanchez(ds28677 homework 25 Turner(58220 This...

This preview shows pages 1–3. Sign up to view the full content.

sanchez (ds28677) – homework 25 – Turner – (58220) 1 This print-out should have 13 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 (part 1 of 2) 10.0 points A skater spins with an angular speed of 17 . 9 rad / s with his arms outstretched. He lowers his arms, decreasing his moment of in- ertia from 43 kg · m 2 to 36 kg · m 2 . a) Calculate his initial rotational kinetic energy. Correct answer: 6888 . 81 J. Explanation: Basic Concepts: L = KE = 1 2 2 Given: I i = 43 kg · m 2 I f = 36 kg · m 2 ω i = 17 . 9 rad / s Solution: KE i = 1 2 I i ω 2 i = 1 2 (43 kg · m 2 )(17 . 9 rad / s) 2 = 6888 . 81 J 002 (part 2 of 2) 10.0 points b) Calculate his final rotational kinetic en- ergy. Correct answer: 8228 . 31 J. Explanation: Solution: Angular momentum of the system is con- served, so I f ω f = I i ω i ω f = I i ω i I f KE f = 1 2 I f parenleftbigg I i ω i I f parenrightbigg 2 = 1 2 I 2 i ω 2 i I f = 1 2 (43 kg · m 2 ) 2 (17 . 9 rad / s) 2 36 kg · m 2 = 8228 . 31 J 003 (part 1 of 3) 10.0 points Assume: The small objects are point parti- cles. The system of nine small 6 kg objects is rotating at an angular speed of 7 rad / s. The objects are connected by light, flexible spokes that can be lengthened or shortened. x y 6 kg 6 kg 6 kg 6 kg 6 kg 6 kg 6 kg 6 kg 6 kg 7 r a d / s 8 m What is the initial angular momentum of the object? Note: An effect similar to this ocurred in the early stages of the formation of our Galaxy. As the massive cloud of dust and gas that was the source of the stars and planets contracted, an initially small angular speed increased with time. Correct answer: 24192 kg m 2 / s. Explanation: BasicConcepts: The angular momentum is L = I ω = ( M r 2 ) ω . With no external torques, angular momentum is concerved.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
sanchez (ds28677) – homework 25 – Turner – (58220) 2 Let : m = 6 kg , r 1 = 8 m , r 2 = 9 m , and ω 1 = 7 rad / s .
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 5

Homework 25 - sanchez(ds28677 homework 25 Turner(58220 This...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online