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Ch2-HW2-solutions (1)

# Ch2-HW2-solutions (1) - schopper(as55864 Ch2-HW2...

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schopper (as55864) – Ch2-HW2 – haley – (56465) 1 This print-out should have 12 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. 001(part1of2)5.0points You’re driving on a straight road (in the + x direction) at a constant speed of 27 m / s. In 9 s, you speed up to 45 m / s to pass a truck. Assuming that your car speeds up at a con- stant rate (constant force by the road on the tires), what is your average x component of velocity v avg ,x during this maneuver? Correct answer: 36 m / s. Explanation: Since the car speeds up at a constant rate, we just need to consider the endpoints, when the car was traveling v i,x = 27 m / s and v f,x = 45 m / s . We calculate the average x component of ve- locity as follows: v avg ,x = v i,x + v f,x 2 = 27 m / s + 45 m / s 2 = 36 m / s . 002(part2of2)5.0points How far do you go during this maneuver? Correct answer: 324 m. Explanation: Again, the fact that the acceleration is con- stant simplifies things. We can just treat this situation as though we were actually moving at the average speed for the 9 s interval: Δ x = = v avg ,x Δ t = (36 m / s)(9 s) = 324 m . 003(part1of3)4.0points On a straight road (taken to be in the + x direction) you drive for an hour at v 1 ,x = 60 km / h , then quickly speed up to v 2 ,x = 115 km / h and drive for an additional two hours. How far do you go (Δ x )? Correct answer: 290 km. Explanation: To find the total distance traveled, we have to consider the two speeds separately: Δ x = v 1 ,x Δ t 1 + v 2 ,x Δ t 2 = (60 km / h)(1 h) + (115 km / h)(2 h) = 290 km .

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