# ec - Extra Credit Problems Physics 1 Mr Kiledjian 1 A rock...

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Extra Credit Problems Physics 1 Mr. Kiledjian 1) A rock is dropped from rest into a well. The sound of the splash is heard 3.25 seconds after the rock is released from rest. The speed of sound in air is 336 m/s. How far below the top of the well is the surface of the water? (Chapter 2, #60) Answer: H = 47.39 meters 2) Setting a new world record in a 100 meter race, Maggie and Judy cross the finish line in a dead heat, both taking 10.2 seconds. Accelerating uniformly, Maggie took 2 seconds and Judy took 3 seconds to attain maximum speed, which they maintained for the rest of the race. a) What was the acceleration of each sprinter? b) What were their respective maximum speeds? c) Which sprinter was ahead at the 6 second mark, and by how much? (Chapter 2, #53) Answer: a) 5.43 m/s 2 and 3.83 m/s 2 b) 10.9 m/s and 11.5 m/s c) Maggie by 2.62 meters 3) The acceleration of a marble in a certain fluid is proportional to the speed of the marble squared, and is given by a = -3.00v 2 for v > 0. If the marble enters this fluid with a speed of 1.50 m/s, how long will it take before the marble’s speed is reduced to half of its initial value? Answer: .222 seconds 4) A pirate has buried his treasure on an island with five trees, located at the following points: A (30 m, -20 m), B (60 m, 80 m), C (-10 m, -10 m), D (40 m, -30 m), and E (-70 m, 60 m). His ship’s log instructs you to start at tree A and move toward tree B, but to cover only half the distance between A and B. Then move toward tree C, covering one third the distance between your current location and C. Next, move toward D, covering one fourth the distance between where you are and D. Finally, move towards E, covering one fifth the distance between you and E, stop, and dig. What are the coordinates of the point where his treasure is buried? (Chapter 3, #59) Answer: (10 m, 16 m) 5) A skier leaves the ramp of a ski jump with a velocity of 10.0 m/s, 15 degrees above the horizontal (this is actually a Winter Olympics sport). The slope of the mountain is inclined at 50 degrees and air resistance is negligible. Find a) the distance from the ramp to where the jumper lands b) the velocity components just before the landing. (Chapter 4, #59) Answer: a) 43.2 meters b) v x = 9.66 m/s v y = -25.5 m/s

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6) An enemy ship is on the east side of a mountain island. The enemy ship has maneuvered to within 2,500 meters of the 1,800 meter-high mountain peak and can shoot projectiles with an initial speed of 250 m/s. If the western shoreline is horizontally 300
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ec - Extra Credit Problems Physics 1 Mr Kiledjian 1 A rock...

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