121%20Exam%201

121%20Exam%201 - Physics 121 Name 9/ 1 4/07 Section 1. A...

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Unformatted text preview: Physics 121 Name 9/ 1 4/07 Section 1. A ball rolls up and back down a straight incline as shown. In the following, assume that the x-axis is along the incline positive to the right. a. On the axes provided, sketch qualitatively correct graphs of position vs. time, velocity vs. time, and acceleration vs. time for the motion of the ball up and back down the incline. (Get the shapes right, but don’t worry about numbers. Be sure to assume the same time scale for each graph, though.) (6 points) (b)-(e) lt’s observed that the ball'begins up the incline with a speed of 6.0 m/s, and slows down at a constant rate to 2.0 m/s in 8.0 s. (That encompasses only part of the motion up the incline, of course.) b. What’s the speed of the ball 0.50 s after it begins up the incline? (2 points) ‘v 8.0: I. Exam 1 Turnaround K point 9.9;, a; a rifle/st c. At what time does the ball turn around? (2 points) . E 4’ ‘0 V: of“ Md'v; lam/3’ ’2) S7“! ' ’5 d. At half of that time (your result for a has the ball traveled halfivay t0 the turnaround point, more than halfivay t0 the turnaround point, or less than halfivay t0 the turnaround point? Explain your reasoning. (2 points) . ,. 0" “J A Just? 6 .r so 50- u-Lu {4 0w". a. e. Determine how far up the incline me Ball trav . points) ff? J “was )M'r‘(6*u)/“: 3-0 ,c-t *I? ' I -___1__.-;_..__-A__.__..__: Name Section 2. An object moves with constant acceleration according to the position vs. time graph at right. For (a)-(e), give the time, or interval of time, during which the object’s motion fits the given description. (If the object never moves as described, say so explicitly.) In each case, briefly explain your reasoning. a. The object has positiv velocity. (2 points) 2- r: in s a" —I% ’ a34- b. The object has positive acceleration. (2 poi ) O— 5: —«v- Slowly {m O-l: c. The object 1s speeding up. (2 points), _+Q. d. The object has zero velocity. ( points) if ’04». e. The object has zero acceleration. (2 points) ~ ' b ’74.»..- M M 4', ‘Jw’ “‘r. “I- ' f. Determine the average velocity for the entire motion. 3 points) «=Aoc_n—g ” a? " f: g. Is the average speed for the entire motion greater than, less than, or equal to the magnitude of the average velocity for the entire motion? Explain. (2 pom 3700.]: Name Section 3. An object moves along a line according to the velocity vs. time graph below. a. On the axes below create a graph of acceleration vs. time for this motion. Make it quantitatively correct; i.e., get the numbers right. (5 points) *VN [3* 0-1:: 3 "" b. How far does the object travel during the entire motion? (5 points) am; 5v.“ v.94. UMP-'1 .32" Name Section 4. Train platform. You want to visit your friend in New York over winter break. To save money, you decide to travel there by train. But you are late finishing your physics final, so you are late in arriving at the train station. You run as fast as you can, but just as you reach one end of the platform, your train is 30 meters ahead of you down the platform and traveling at a constant speed of 5.0 m/s. You run at your top speed of 8.0 m/s. You can run along the platform for 50 meters before you reach a barrier. Will you catch your train? (For full credit your solution must include qualitatively correct graphs of position vs. time and velocity vs. time, a description of your plan for solving the problem, and an answer to the question posed in the problem points) . 'fiofar you. J: '03 5‘ d:dhy’CJB‘ 0‘: ...
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This note was uploaded on 02/29/2008 for the course PHYS 121 taught by Professor Angerson during the Fall '07 term at UMBC.

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121%20Exam%201 - Physics 121 Name 9/ 1 4/07 Section 1. A...

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