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Unformatted text preview: fryer (vdf96) 2D kinematics graves (6) 1 This print-out should have 35 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 (part 1 of 3) 10.0 points A ball is thrown and follows the parabolic path shown. Point Q is the highest point on the path and points P and R are the same height above the ground. Q R P How do the speeds of the ball at the three points compare? Air friction is negligible. 1. bardbl vectorv Q bardbl < bardbl vectorv R bardbl < bardbl vectorv P bardbl 2. bardbl vectorv P bardbl < bardbl vectorv Q bardbl < bardbl vectorv R bardbl 3. bardbl vectorv Q bardbl < bardbl vectorv P bardbl = bardbl vectorv R bardbl correct 4. bardbl vectorv P bardbl = bardbl vectorv R bardbl < bardbl vectorv Q bardbl 5. bardbl vectorv R bardbl < bardbl vectorv Q bardbl < bardbl vectorv P bardbl Explanation: The speed of the ball in the x-direction is constant. Because of gravitational accelera- tion, the speed in the y-direction is zero at point Q . Since points P and R are located at the same point above ground, by symmetry they have the same vertical speed component (though they do not have the same velocity), so v Q < v P = v R . 002 (part 2 of 3) 10.0 points Which diagram best indicates the direction of the acceleration, if any, on the ball at point R ? 1. 2. 3. 4. 5. 6. correct 7. 8. The ball is in free fall and there is no acceleration at any point on its path. 9. Explanation: Since air friction is negligible, the only ac- celeration on the ball after being thrown is that due to gravity, which acts straight down. 003 (part 3 of 3) 10.0 points Which diagram best indicates the direction of the net force, if any, on the ball at point Q ? 1. 2. 3. fryer (vdf96) 2D kinematics graves (6) 2 4. correct 5. 6. 7. 8. 9. The ball is in free-fall and there is no acceleration at any point on its path. Explanation: By Newtons second law, the force is in the direction of the acceleration (downward). 004 (part 1 of 4) 10.0 points A plane is flying horizontally with speed 107 m / s at a height 6680 m above the ground, when a package is dropped from the plane. The acceleration of gravity is 9 . 8 m / s 2 . Neglecting air resistance, when the package hits the ground, the plane will be 1. directly above the package. correct 2. behind the package. 3. ahead of the package. Explanation: Both have the same velocity at the time of release. Gravitational acceleration does not change horizontal velocity, so the plane will be directly above the package. 005 (part 2 of 4) 10.0 points What is the horizontal distance from the re- lease point to the impact point? Correct answer: 3950 . 7 m. Explanation: For the vertical fall, h = 1 2 g t 2 , or t = radicalBigg 2 h g . The horizontal distance traveled is x = v t = v radicalBigg 2 h g = (107 m / s) radicalBigg 2 (6680 m) 9 . 8 m / s 2 = 3950 . 7 m ....
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