phy 131 midterm3 with solutions

phy 131 midterm3 with solutions - PHY 131.05 Midterm Exam...

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Unformatted text preview: PHY 131.05 Midterm Exam NAME: Tuesday, February 5, 2008 Directions: You have 75 minutes. Support your answers. Correct answers with no or unsatisfactory explanation, or supporting calculations (whatever is applicable) will not receive any credit. You are allowed to use one page (only one side) formula sheet, and a calculator. Solve the questions on the same page. If necessary, you can use the back of the page as well. 1 A stone thrown upward [20 pts] A stone is thrown upward with 10.0 m/s at t=0. Assume there is no air resis- tance. (a) What is the acceleration (magnitude and direction) at t=1.50 s? (b) Where is the object at t=1.50 s? (c) Which direction does the object move at t=1.50 s? ( d) Is the object slowing down or speeding up at t=1.50 s? Figure 1: Figure for Question 1. 2 Velocity and Acceleration [20 pts] Motion diagram for an object moving in a curve is givean/L‘Q’ (a) Find the direction of the acceleration at point 4. (b)Find the direction of the acceleration at point 10. Position, meters tA t3 Q Q, Time, seconds Figure 2: Figure for Question 2. 3 Position '03 time graph [20 pts] Position vs time graph for two cars moving along the same straight track are given (one solid, the other dashed). (a) At what time(s) or in which time interval(s) have these cars met at a point along their tracks? (Your answer should be in the form ” at 75A” or ”some time between 75,; and t3”) Explain. ) At what time(s) or in which time interval(s) have these cars had the same speed? (Your answer should be in the form ”at 73;” or ”some time between 15A and t3”) Explain. (a) #4; fat: xi/Leif We: 1% / “HY jaw. WW”? 4 Galieo: The Movie [20 pts] Because of your physics background, you have been hired as a consultant for a new movie about Galileo. In one scene, he climbs up to the top of a tower and, in fiustration over the people who ridicule his theories, throws a rock at a group of them standing on the ground. The rock leaves his hand at 30° from the horizontal. The script calls for the rock to land 15 In from the base of the tower near a group of his detractors. It is important for the script that the rock take precisely 3.0 seconds to hit the ground so that there is time for a good expressive close-up. The set coordinator is concerned that the rock will hit the ground with too much speed causing cement chips from the plaza to injure one of the high priced actors. You are told to calculate that speed. (First draw a picture to visualize the situation.) 29 a: 2,5», \\\ M to Figure 3: Figure for Question 1. 5 Vector Algebra, [20 pts] Two force vectors are shown in the graph. Magnitude of A is 8.00 N, and that of B is 10.0 N. (a) Find D = E — 2K, and express in component form. (b) Find the magnitude of D. (c) Find the direction of D and Show it in the coordinate system. 9 -: ~ Mogso“ 9:3 ; , Hamid? R j 123$ng Q? t; IBQJ525 ._ F5”, 5 / fivZ’g-L; Poo: 3;” Him/33] d *2, . , / i 052% g arowwetfl g “7‘ Figure 4: . 6 Circular motion[20 pts] A ball attached to a 2.50 1n—1ong string is rotated in uniform circular motion, as shown in the figure, with speed of 5.00 m/s. As the ball is moving from A to L B, the string breaks at B. r W ’~ (3.) What is the total acceleration of the ball right before the string breaks? é waif/y” AAWW) (b) What is the total acceleration of the ball right after the string breaks? (c) Roughly sketch how the ball will move after the string breaks. PM} W1 ””7 (a) Bari/c es SW WW ( 7m _ a ‘ 7 A car accelerating on a circular track: [Emtra Credit: 20 pts] ‘ A car starts from rest on a curve with a radius of 190 m and accelerates at 1.30 m/sg. How many revolutions will the car have gone through When the magnitude of its total acceleration is 2.10 111/32? .7. . V é ' :’ E: 33 (2%.: \‘1 Q ”,3 (My , , ’/ f} 33 D V ' f”\ 0 f “ {3/6) ' ' .r ...
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