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oldmidterm1 #1

# oldmidterm1 #1 - hinojosa(jlh3938 oldmidterm1 01...

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hinojosa (jlh3938) – oldmidterm1 01 – Turner – (58185) 1 This print-out should have 20 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001 10.0 points Consider a piece of string which is placed along the x -axis. Let Δ m be the mass of a segment of the string and Δ x the length of this segment. The linear mass density, μ , of a piece of string is defined as μ = Δ m Δ x . Denote ρ to be its mass density defined as ρ = mass volume and A its cross sectional area. Let us write μ = ρ x A y . Using dimensional analysis, determine the equations which enable one to solve for x and y . 1. x = 1 , 2 y 3 x = 1 2. x = 1 , 3 x + 2 y = 1 3. x = 1 , 2 y + 3 x = 1 4. x = 1 , 2 y + 3 x = 1 5. x = 1 , 2 y 3 x = 1 6. x = 1 , 2 y 3 x = 1 7. x = 1 , 2 y 3 x = 1 8. x = 1 , 2 y 3 x = 1 correct 9. x = 1 , 3 x + 2 y = 1 10. x = 1 , 2 y 3 x = 1 Explanation: [ μ ] = [ ρ x A y ] ML 1 = M x L 3 x L 2 y = M x L 2 y 3 x Equating both sides yields the equations x = 1 , 2 y 3 x = 1 002 10.0 points Two points in a rectangular coordinate sys- tem have the coordinates (4 . 6 cm, 5 . 9 cm) and ( 8 . 8 cm, 4 . 5 cm). Find the distance between these points. Correct answer: 13 . 4729 cm. Explanation: Given : x 1 = 4 . 6 cm , y 1 = 5 . 9 cm , x 2 = 8 . 8 cm , and y 2 = 4 . 5 cm . Using the Pythagorean Theorem, d = radicalBig x ) 2 + (Δ y ) 2 = radicalBig ( x 2 x 1 ) 2 + ( y 2 y 1 ) 2 = radicalBig [4 . 6 cm ( 8 . 8 cm)] 2 + (4 . 5 cm 5 . 9 cm) 2 = 13 . 4729 cm . 003 10.0 points Ann is driving down a street at 64 km / h. Suddenly a child runs into the street. If it takes Ann 0 . 718 s to react and apply the brakes, how far will she have moved before she begins to slow down? Correct answer: 12 . 7645 m. Explanation: d = v t = (64 km / h) (0 . 718 s) = 12 . 7645 m . Dimensional analysis for d : km h · s 1 · 1 h 3600 s · 1000 m 3600 km = m

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hinojosa (jlh3938) – oldmidterm1 01 – Turner – (58185) 2 004 10.0 points The graph shows position as a function of time for two trains running on parallel tracks. At time t = 0 (origin) the position of both trains is 0. position time t B B A Which is true? 1. Both trains speed up all the time 2. Both trains have the same velocity at some time before t B correct 3. Somewhere before time t B , both trains have the same acceleration 4. At time t B , both trains have the same velocity 5. In the time interval from t =0 to t = t B , train B covers more distance than train A Explanation: The slope of the curve B is parallel to line A at some point t < t B . 005 10.0 points Suppose the position equation for a moving object is given by s ( t ) = 3 t 2 + 2 t + 5 where s is measured in meters and t is mea- sured in seconds. Find the velocity of the object when t = 2. 1. 13 m/sec 2. 14 m/sec correct 3. 10 m/sec 4. 6 m/sec 5. None of these Explanation: s ( t ) = 3 t 2 + 2 t + 5 The velocity is v ( t ) = s ( t ) = 6 t + 2 and v (2) = 14. 006 10.0 points A ranger in a national park is driving at 49 km / h when a deer jumps onto the road 61 m ahead of the vehicle. After a reaction time of t s, the ranger applies the brakes to produce an acceleration of 3 . 8 m/s 2 .
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oldmidterm1 #1 - hinojosa(jlh3938 oldmidterm1 01...

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