# hw07 - alexander(jra2623 homework 07 Turner(92510 This...

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alexander (jra2623) – homework 07 – Turner – (92510) 1 This print-out should have 11 questions. Multiple-choice questions may continue on the next column or page – fnd all choices beFore answering. 001 (part 1 oF 4) 10.0 points Consider the setup oF a gun aimed at a target (such as a monkey) as shown in the fgure below. The target is to be dropped From the point A at t = 0, the same moment as the gun is fred. The bullet hits the target at a point P . Let the initial speed oF the bullet be v 0 = 107 m / s, let the angle between the vector V v 0 and the horizontal ( x -) direction be θ = 44 . 8 and let AB = 94 . 4 m. The distance d = OB is the x -coordinate oF the target. Denote the time taken to hit the target by t . v 0 θ h x y O A B P The acceleration oF gravity is 9 . 8 m / s 2 . This time is given by 1. t = d v 0 cos θ . correct 2. t = d v 0 . 3. t = d v 0 tan θ . 4. t = d v 0 sin θ . 5. t = d v 0 cot θ . Explanation: Basic Concepts: Constant acceleration: x - x 0 = v 0 t + 1 2 at 2 (1) v = v 0 + at (2) Solution: Think oF this two-dimensional motion as two one-dimensional trajectories, one in the x and one in the y -direction. The horizontal ( x ) initial velocity is v 0 x = v 0 cos θ . The x -motion is unaccelerated (gravity only a±ects the y -motion) so equation (1) gives d = v 0 x t + 0 . Thus t = d v 0 x = d v 0 cos θ . 002 (part 2 oF 4) 10.0 points Assume: Up is the positive direction. With the time taken to hit the target given by t , the vertical ( y -) component oF the veloc- ity oF the bullet is 1. v y = - g t 2. v y = v 0 sin θ + g t 3. v y = v 0 cos θ + g t 4. v y = - v 0 cos θ + g t 5. v y = v 0 cos θ - g t 6. v y = g t 7. v y = v 0 sin θ - g t correct 8. v y = - v 0 sin θ - g t 9. v y = - v 0 cos θ - g t 10. v y = - v 0 sin θ + g t Explanation: The vertical ( y ) initial velocity is given by v 0 y = v 0 sin θ We take positive direction upward, so a = - g and equation (2) gives us For the vertical component oF the velocity at P v Py = v 0 y - g t = v 0 sin θ - g t .

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alexander (jra2623) – homework 07 – Turner – (92510) 2 003 (part 3 of 4) 10.0 points The height BP where the collision takes place is Correct answer: 86 . 7185 m. Explanation:
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hw07 - alexander(jra2623 homework 07 Turner(92510 This...

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