s2a10 - Physics E-1a Solutions Homework #2 Fall 2010 MC 5...

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Physics E-1a Solutions Homework #2 Fall 2010 MC 5 The answer is a) The quickest way across the river is to head directly across the river. All of the boy’s velocity is directed towards the other shore. Of course his velocity with respect to the shore is the sum of his velocity vector and the river’s velocity vector. So the boy crosses the river quickly but ends up down stream a bit. MC 6 The answer is c) The boy must have a component of his velocity, with respect to the shore, up river or north. The northern component of the boy’s velocity must be equal to southern velocity of the river (1m/s). The other component of the boy’s velocity is east, across the river. MC 7 The answer is e) The horizontal or x component of the footballs velocity is constant throughout the trajectory so the speed of the football is a minimum when the vertical or y component is zero. The y component is zero when the football is at its maximum height, halfway along the x-axis, or 20 meters from where it was kicked. MC 11 The answer is d) The highest point in a trajectory (point A) always has the minimum velocity. The acceleration is constant throughout the flight of the ball. 30. Strategy Use the definitions of average speed and average velocity. Solution (a) Find the runner’s average speed.
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This note was uploaded on 10/26/2011 for the course PHYSICS E-1b taught by Professor Wolfgangrueckner during the Spring '11 term at Harvard.

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s2a10 - Physics E-1a Solutions Homework #2 Fall 2010 MC 5...

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