# exam2sol - Version 017 exam2 markert(58840 This print-out...

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Version 017 – exam2 – markert – (58840) 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 Mary weighs 471 N and she walks down a ±ight oF stairs to a level 6 . 6 m below her starting point. What is the change in Mary’s potential en- ergy? 1. -2227.5 2. -2557.8 3. -2368.8 4. -3220.0 5. -3108.6 6. -3383.5 7. -2786.4 8. -3069.0 9. -2141.1 10. -1935.1 Correct answer: 3108 . 6 J. Explanation: We can let the initial potential energy be 0. The change in potential energy is Δ U = U f U i = mg ( h ) = (471 N)(6 . 6 m) = 3108 . 6 J . 002 10.0 points The amount oF work done by two boys who apply 230 N oF Force in an unsuccessFul at- tempt to move a stalled car is 1. 230 N · m. 2. 230 N. 3. 460 N. 4. 460 N · m. 5. 0. correct Explanation: W = F d , so with an unsuccessFul attempt to move the car, no work was done. 003 10.0 points A car with mass 1212 kg, moving at 40 m / s, strikes a(n) 2738 kg car at rest. IF the two cars stick together, with what speed do they move? 1. 11.493 2. 13.0147 3. 6.96477 4. 9.87273 5. 8.99133 6. 8.55566 7. 12.2734 8. 12.602 9. 13.4361 10. 6.51634 Correct answer: 12 . 2734 m / s. Explanation: Basic concepts Momentum oF any object is p = mv The collision is inelastic, and by conservation oF momentum, p before = p after m 1 v o + 0 = ( m 1 + m 2 ) v f v f = m 1 v o ( m 1 + m 2 ) 004 10.0 points ²ive ramps lead From the ground to the second ±oor oF a workshop, as sketched below. All fve ramps have the same height; ramps B, C, D and E have the same length; ramp A is longer than the other Four. You need to push a heavy cart up to the second ±oor and you may choose any one oF the fve ramps.

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Version 017 – exam2 – markert – (58840) 2 A B C D E Assuming no frictional forces on the cart, which ramp would require you to do the least work? 1. Unable to determine without knowing the exact proFles of ramps C, D or E. 2. Ramp D. 3. Same work for all Fve ramps. correct 4. Ramp E. 5. Same work for ramps B, C, D or E; more work for ramp A. 6. Ramp C. 7. Same work for the straight ramps A and B; less work for ramps C, D, and E. 8. Ramp B. 9. Ramp A. Explanation: Let h be the height of the ramps. Since there is no friction, we can use the work- energy theorem. W
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exam2sol - Version 017 exam2 markert(58840 This print-out...

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