Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

Published by Pearson
ISBN 10: 0133942651
ISBN 13: 978-0-13394-265-1

Chapter 10 - Interactions and Potential Energy - Exercises and Problems - Page 258: 44

Answer

$x = 42.7~m$

Work Step by Step

We can use conservation of energy to find the speed at the end of the ramp: $U_{g2}+K_2 = U_{g1}+K_1$ $K_2 = U_{g1}-U_{g2}+0$ $\frac{1}{2}mv_2^2 = mgh_1-mgh_2$ $v_2^2 = 2g~(h_1-h_2)$ $v_2 = \sqrt{2g~(h_1-h_2)}$ $v_2 = \sqrt{(2)(9.8~m/s^2)~(25~m-3~m)}$ $v_2 = 20.765~m/s$ According to the geometry, the direction of motion at the end of the ramp is $30^{\circ}$ above the horizontal. For the next part of the question, we can let $~~v_0= 20.765~m/s$ We can find the time of flight $y = y_0+v_{0y}t+\frac{1}{2}a_yt^2$ $\frac{1}{2}a_yt^2+v_0~sin(30^{\circ})t+y_0 = 0$ $-4.9~t^2+(20.765)~sin(30^{\circ})t+3 = 0$ $-4.9~t^2+10.38~t+3 = 0$ We can use the quadratic formula: $t = \frac{-b\pm \sqrt{b^2-4ac}}{2a}$ $t = \frac{-(10.38)\pm \sqrt{(10.38)^2-(4)(-4.9)(3)}}{(2)(-4.9)}$ $t = -0.26~s, 2.376~s$ We can choose the positive solution. Then $t = 2.376~s$ We can find the horizontal distance traveled in this time: $x = v_{0x}~t$ $x = v_0~cos~30^{\circ}~t$ $x = (20.765~m/s)~(cos~30^{\circ})~(2.376~s)$ $x = 42.7~m$
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