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Unformatted text preview: sousse (res2468) – HW 4 – Kleinman – (58225) 1 This print-out should have 31 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. This HW covers Chapters 5 and 6. 001 10.0 points A heavily loaded freight train moves with constant velocity. What is the relationship between the net force on the first car ( F 1 ) and the net force on the last car ( F 2 )? 1. Unable to determine. 2. F 1 < F 2 3. F 1 = F 2 correct 4. F 1 > F 2 Explanation: The net force on each car is zero because the train moves with constant velocity (no acceleration). 002 10.0 points A toy car is given a quick push so that it rolls up an inclined ramp. After it is released, it rolls up, reaches its highest point and rolls back down again. Friction is so small it can be ignored. What net force acts on the car? 1. Net increasing force down the ramp 2. Net increasing force up the ramp 3. Net force of zero 4. Net decreasing force down the ramp 5. Net constant force up the ramp 6. Net constant force down the ramp cor- rect 7. Net decreasing force up the ramp Explanation: The net force is the component of gravity along the incline; it is constant and acts down the ramp. 003 10.0 points Despite a very strong wind, a tennis player manages to hit a tennis ball with her racquet so that the ball passes over the net and lands in her opponents court. Consider the following forces: 1 - A downward force of gravity. 2 - A force by the “hit”. 3 - A force exerted by the air. Which of the above forces is (are) acting on the tennis ball after it has left contact with the racquet and before it touches the ground? 1. 1 only 2. 1, 2 and 3 3. 2 and 3 4. 1 and 2 5. 1 and 3 correct Explanation: After the contact with the racquet, only the air resistance and the gravity act upon the ball. 004 (part 1 of 2) 10.0 points The wind exerts a force of 218 N North on a sailboat, while the water exerts a force of 158 N West on the sailboat. What is the magnitude of the net external force on the sailboat? Correct answer: 269 . 236 N. Explanation: Let : F x = F water = − 158 N and F y = F wind = 218 N . sousse (res2468) – HW 4 – Kleinman – (58225) 2 218 N 158 N v Scale: 100 m θ Thus F net = radicalBig F 2 x + F 2 y = radicalBig ( − 158 N) 2 + (218 N) 2 = 269 . 236 N . 005 (part 2 of 2) 10.0 points How many degrees west of north is this net external force directed? Correct answer: 35 . 9335 ◦ . Explanation: tan θ = F x F y θ = tan − 1 parenleftbigg F x F y parenrightbigg = tan − 1 parenleftbigg − 158 N 218 N parenrightbigg = − 35 . 9335 ◦ , which is 35 . 9335 ◦ to the west of north. keywords: 006 10.0 points The position of a toy locomotive moving on a straight track along the x-axis is given by the equation x = t 5 − 6 t 2 + 9 t, where x is in meters and t is in seconds....
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This note was uploaded on 04/08/2009 for the course PHY 303K taught by Professor Turner during the Spring '08 term at University of Texas.
- Spring '08