# hw15 - Muraj Hamza – Homework 15 – Due 4:00 am – Inst...

This preview shows pages 1–2. 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: Muraj, Hamza – Homework 15 – Due: Feb 27 2006, 4:00 am – Inst: Florin 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 2) 10 points A person lifts a 4.3 kg cement block a vertical distance of 1.1 m and then carries the block horizontally a distance of 8.1 m. The acceleration of gravity is 9 . 81 m / s 2 . a) Determine the work done by the person in the process. Correct answer: 46 . 4013 J. Explanation: Basic Concept: W = F d cos θ Given: m = 4 . 3 kg d 1 = 1 . 1 m d 2 = 8 . 1 m g = 9 . 81 m / s 2 θ 1 = 0 ◦ θ 2 = 90 ◦ Solution: W person = F g d 1 cos θ 1 + F g d 2 cos θ 2 = mg d 1 cos0 ◦ + mg d 2 cos90 ◦ = mg d 1 = (4 . 3 kg) ( 9 . 81 m / s 2 ) (1 . 1 m) = 46 . 4013 J . 002 (part 2 of 2) 10 points b) Determine the work done by the force of gravity in the process. Correct answer:- 46 . 4013 J. Explanation: Given: θ 1 = 180 ◦ Solution: W gravity = F g d 1 cos θ 1 + F g d 2 cos θ 2 = mg d 1 cos180 ◦ + mg d 2 cos90 ◦ =- mg d 1 =- (4 . 3 kg)(9 . 81 m / s 2 )(1 . 1 m) =- 46 . 4013 J . 003 (part 1 of 1) 10 points A car and driver weighing 7120 N passes a sign stating “Bridge Out 25 . 3 m Ahead.” She slams on the brakes, and the car decelerates at a constant rate of 12 . 3 m / s 2 . The acceleration of gravity is 9 . 8 m / s 2 . What is the magnitude of the work done stopping the car if the car just stops in time to avoid diving into the water? Correct answer: 226089 J. Explanation: The mass of the car is m = W g = 7120 N 9 . 8 m / s 2 = 726 . 531 kg . The force exerted by the brake is F = ma = (726 . 531 kg)(12 . 3 m / s 2 ) = 8936 . 33 N . Therefore, the work done by the brake on the car is W = F x = (8936 . 33 N)(25 . 3 m) = 226089 J ....
View Full Document

{[ snackBarMessage ]}

### Page1 / 4

hw15 - Muraj Hamza – Homework 15 – Due 4:00 am – Inst...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online