# sol09 - during the 14 s required to fall to the ground We...

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PHYSICS 103 Chapter 4 -- HW #9 Questions 20. Because the book slides along a frictionless table at a constant velocity, we know that there are no horizontal forces acting on the book. Because the book does not accelerate in the vertical direction, the normal force and the gravitational force must add to zero. When the book sails off the edge of the table, the normal force disappears while the gravitational force continues to act. This is the net force that causes the book to fall freely. 24. As the vertical and horizontal motions are independent of each other, the rock that is thrown horizontally will still take 2 seconds to reach the surface of the Moon. Exercise 14. Remember that the horizontal and vertical motions are independent of each other. The horizontal motion is motion with a constant speed—therefore, the horizontal component of the velocity remains constant. The range is just the distance the water travels horizontally
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Unformatted text preview: during the 14 s required to fall to the ground. We can use this to find the initial horizontal velocity as we did in lab. 50 m 3.57 s 14 s h h r v t r v t = = = = 16. Once again, we must remember that the vertical and horizontal motions are independent of each other. We begin by looking at the vertical motion. Because the ball loses 10 m/s in vertical speed each second, we can reason that it will take 3 s to reach the top of its path (the instantaneous speed is zero at the top). Symmetry tells us that it will also take 3 s to fall back down to the same height. Therefore, the ball is in the air for a total of 6 s. Mathematically, 2 0 30 m/s 3s = 6 s 10 m/s up v t t a ∆-= = = ⇒-where we chose the up direction to be positive. We now use this time to calculate the range of the ball. ( 29 ( 29 6 m s 6 s 36 m R vt = = =...
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