This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.
View Full Document
Unformatted text preview: oldhomewk 01 YOO, HEE Due: Jan 17 2008, 4:00 am 1 Question 1, chap 1, sect 5. part 1 of 1 10 points A newly discovered giant planet has an av erage radius 17 times that of the Earth and a mass 181 times that of the Earth. Calculate the ratio of the new planets den sity to the Earths density. Correct answer: 0 . 036841 (tolerance 1 %). Explanation: Let : R n = 17 R E and m n = 181 m E . Density is the ratio of mass to volume, = m V . A spherical planet of average radius R has volume 4 3 R 3 and hence density = m 4 3 R 3 . For two planets of respective radii R 1 and R 2 and masses m 1 and m 2 we have 1 2 = m 1 4 3 R 3 1 m 2 4 3 R 3 2 = parenleftbigg m 1 m 2 parenrightbigg parenleftbigg R 1 R 2 parenrightbigg 3 = 181 (17) 3 = . 036841 . Question 2, chap 1, sect 5. part 1 of 1 10 points A sphere of metal has a radius of 5 . 7 cm and a density of 6 . 81 g / cm 3 . What is the mass of the sphere? Correct answer: 5282 . 75 g (tolerance 1 %). Explanation: Let : r = 5 . 7 cm and = 6 . 81 g / cm 3 . Density is mass per unit volume, so = m V m = V = 4 3 r 3 = ( 6 . 81 g / cm 3 ) 4 3 (5 . 7 cm) 3 = 5282 . 75 g . Question 3, chap 1, sect 99. part 1 of 1 10 points A cylinder, 20 cm long and 8 cm in radius, is made of two different metals bonded end toend to make a single bar. The densities are 5 g / cm 3 and 6 . 1 g / cm 3 . 2 c m 8 cm What length of the lighter metal is needed if the total mass is 21565 g? Correct answer: 13 . 4041 cm (tolerance 1 %). Explanation: Let : = 20 cm , r = 8 cm , 1 = 5 g / cm 3 , 2 = 6 . 1 g / cm 3 , and m = 21565 g . oldhomewk 01 YOO, HEE Due: Jan 17 2008, 4:00 am 2 Volume of a bar of radius r and length is V = r 2 and its density is = m V = m r 2 so that m = r 2 x x r Let x be the length of the lighter metal; then x is the length of the heavier metal....
View
Full
Document
This note was uploaded on 05/04/2008 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas at Austin.
 Spring '08
 Turner
 Physics, Mass

Click to edit the document details