Exam2-solutions

# Exam2-solutions - Version 040 Exam2 markert (56480) This...

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

Version 040 – Exam2 – markert – (56480) 1 This print-out should have 14 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 10.0 points A rock oF mass m is thrown horizontally o± a building From a height h . The speed oF the rock as it leaves the thrower’s hand at the edge oF the building is v 0 , as shown. m h v 0 m What is the kinetic energy oF the rock just beFore it hits the ground? 1. K f = 1 2 mv 2 0 + mg h correct 2. K f = mg h - 1 2 mv 2 0 3. K f = mg h 4. K f = 1 2 mv 2 0 - mg h 5. K f = 1 2 mv 2 0 Explanation: We can use work-energy theorem, K f - K i = W , where in the present problem, W = ( mg ) h , and K i = 1 2 mv 2 0 . Thus, K f = K i + W = 1 2 mv 2 0 + mg h . Comments For Matter Interaction readers: The energy principle in MI-text is reFerred to as the work-energy theorem in traditional text. Here the work done by the gravitational Force near the surFace oF the earth is given by: W = ( - mg )( - h ) = mg h . 002 10.0 points IF 3.4 J oF work is done in raising a 177 g apple, how Far is it liFted? 1. 2.20315 2. 1.68135 3. 1.47914 4. 1.95611 5. 1.71018 6. 1.13896 7. 1.60514 8. 1.567 9. 2.12324 10. 1.19835 Correct answer: 1 . 95611 m. Explanation: Basic Concepts: W applied = F applied d cos θ = mgd since θ = 0 cos θ = 1. 1 J = 1 N · m F = mg 1 N = 1 kg · m / s 2 Given: W applied = 3 . 4 J m = 177 g g = 9 . 81 m / s 2 Solution: The Force and displacement are parallel, so the distance is given by d = W applied mg = 3 . 4 J (177 g)(9 . 82 m / s 2 ) · 1000 g 1 kg = 1 . 95611 m 003 10.0 points A ball rolls up an incline, slows to a stop and rolls back down. direction oF motion A B C D E ² G

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

View Full Document
Version 040 – Exam2 – markert – (56480) 2 Which of the following represents the di- rection of the ball’s acceleration at the times indicated? 1. A B C D E F G 2. A B C D E F G correct 3. A B C D E F G 4. A B C D E F G 5. A B C D E F G 6. A B C D E F G 7. A B C D E F G Explanation: va = Δ vV Δ t , so va is in the same direction as Δ vV . By subtracting the velocity vectors, one can see that the direction of Δ vV is exactly opposite the direction of vV . Therefore, the direction of va is down the incline at all points. 004
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 10/25/2010 for the course PHY PHYSICS taught by Professor Swinney during the Fall '08 term at University of Texas at Austin.

### Page1 / 6

Exam2-solutions - Version 040 Exam2 markert (56480) 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