HW #1-solutions

# HW #1-solutions - rathbun(rar2954 – HW#1 – Antoniewicz...

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
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: rathbun (rar2954) – 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 63 . 7% of the Earth’s surface is covered with water at average depth of 1 . 57 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: 8 . 2051 × 10 20 kg. Explanation: Let : R = 0 . 637 , h = 1 . 57 mi , ρ = 1000 kg / m 3 , and R e = 6 . 37 × 10 6 m . If the area of Earth covered by water is . 637(4 π R 2 e ), a good approximation of the volume of water covering the earth is V = 0 . 637(4 π R 2 e ) h, and the mass is m = ρ V = 0 . 637 ρ 4 π R 2 e h = 0 . 637 (1000 kg / m 3 ) 4 π (6 . 37 × 10 6 m) 2 × (1 . 57 mi) 1000 m 1 km 1 . 609 km 1 mi = 8 . 2051 × 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. 35 cm 30 cm 3 cm 3 cm What is the mass of a section 0 . 848 m long? The density of iron is 7560 kg / m 3 , the atomic weight of iron is 55 . 85 g / mol and Avogadro’s number is 6 . 02214 × 10 23 atoms / mol. Correct answer: 180 . 787 kg. Explanation: Let : d = 3 cm = 0 . 03 m , w = 35 cm = 0 . 35 m , h = 30 cm = 0 . 3 m , = 0 . 848 m , and ρ = 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 . 35 m) (0 . 03 m) + [0 . 3 m- 2 (0 . 03 m)] (0 . 03 m) = 0 . 0282 m 2 , so the volume of the beam is V = A and the mass is m = ρ V = ρ A = (7560 kg / m 3 )(0 . 0282 m 2 )(0 . 848 m) = 180 . 787 kg . 003 (part 2 of 2) 5.0 points How many atoms are there in this section? Correct answer: 1 . 94937 × 10 27 atoms. Explanation: rathbun (rar2954) – HW #1 – Antoniewicz – (57380) 2 Let : M = 55 . 85 g / mol and N A = 6 . 02214 × 10 23 atoms / mol ....
View Full Document

## This note was uploaded on 03/08/2011 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas.

### Page1 / 5

HW #1-solutions - rathbun(rar2954 – HW#1 – Antoniewicz...

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

View Full Document
Ask a homework question - tutors are online