Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 7 - Kinetic Energy and Work - Questions - Page 170: 10

Answer

The possible graphs are (e), (f), (g), and (h)

Work Step by Step

If the glob is dropped, then $K=0$ at $t=0$, since the initial velocity is zero. As the glob falls, the speed increases with time: $v = gt$ We can write an expression for the kinetic energy at time $t$: $K = \frac{1}{2}mv^2$ $K = \frac{1}{2}m(gt)^2$ $K = \frac{1}{2}mg^2~t^2$ We can see that the kinetic energy starts at 0 and then increases as a function of $t^2$ Graph (f) is a graph for this situation. If the glob is launched horizontally or down, then at $t=0$, $K \gt 0$ and then $K$ increases as a function of $t^2$ Graph (h) is a graph for this situation. If the glob is launched directly up vertically, then at $t=0$, $K \gt 0$ and then $K$ decreases to zero when it reaches maximum height. After this, $K$ increases as a function of $t^2$ Graph (e) is a graph for this situation. If the glob is launched upward with some horizontal component of motion, then at $t=0$, $K \gt 0$. Then $K$ decreases, but remains positive, until it reaches maximum height. After this, $K$ increases as a function of $t^2$ Graph (g) is a graph for this situation. The possible graphs are (e), (f), (g), and (h).
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