physics HW1 - rose (kmr2427) HW #1 Antoniewicz (57380) 1...

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

View Full Document Right Arrow Icon

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

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rose (kmr2427) HW #1 Antoniewicz (57380) 1 This print-out should have 15 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 10.0 points Assuming that 62 . 3% of the Earths surface is covered with water at average depth of 1 . 56 mi, estimate the mass of the water on Earth. One mile is approximately 1.609 km and the radius of the earth is 6 . 37 10 6 m. Correct answer: 7 . 97365 10 20 kg. Explanation: Let : R = 0 . 623 , h = 1 . 56 mi , = 1000 kg / m 3 , and R e = 6 . 37 10 6 m . If the area of Earth covered by water is . 623(4 R 2 e ), a good approximation of the volume of water covering the earth is V = 0 . 623(4 R 2 e ) h, and the mass is m = V = 0 . 623 4 R 2 e h = 0 . 623 (1000 kg / m 3 ) 4 (6 . 37 10 6 m) 2 (1 . 56 mi) 1000 m 1 km 1 . 609 km 1 mi = 7 . 97365 10 20 kg . 002 (part 1 of 2) 5.0 points A structural I beam is made of iron. A view of its cross-section and dimensions is shown. 30 cm 27 cm 3 cm 3 cm What is the mass of a section 0 . 889 m long? The density of iron is 7560 kg / m 3 , the atomic weight of iron is 55 . 85 g / mol and Avogadros number is 6 . 02214 10 23 atoms / mol. Correct answer: 163 . 316 kg. Explanation: Let : d = 3 cm = 0 . 03 m , w = 30 cm = 0 . 3 m , h = 27 cm = 0 . 27 m , = 0 . 889 m , and = 7560 kg / m 3 . w h d d The cross-sectional area of the beam is A = 2 w d + ( h- 2 d ) d = 2(0 . 3 m) (0 . 03 m) + [0 . 27 m- 2 (0 . 03 m)] (0 . 03 m) = 0 . 0243 m 2 , so the volume of the beam is V = A and the mass is m = V = A = (7560 kg / m 3 )(0 . 0243 m 2 )(0 . 889 m) = 163 . 316 kg . 003 (part 2 of 2) 5.0 points How many atoms are there in this section? Correct answer: 1 . 76099 10 27 atoms. Explanation: Let : M = 55 . 85 g / mol and N A = 6 . 02214 10 23 atoms / mol . rose (kmr2427) HW #1 Antoniewicz (57380) 2 The number of moles is n = m M , so the num- ber of atoms is N = n N A = m M N A = 163 . 316 kg 55 . 85 g / mol 1000 g 1 kg (6 . 02214 10 23 atoms / mol) = 1 . 76099 10 27 atoms ....
View Full Document

Page1 / 5

physics HW1 - rose (kmr2427) HW #1 Antoniewicz (57380) 1...

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

View Full Document Right Arrow Icon
Ask a homework question - tutors are online