University Physics with Modern Physics (14th Edition)

Published by Pearson
ISBN 10: 0321973615
ISBN 13: 978-0-32197-361-0

Chapter 3 - Motion in Two or Three Dimensions - Problems - Exercises - Page 93: 3.4

Answer

(a) $v_x(t) = (0.280~m/s)+ (0.0720~m/s^2)~t$ $v_y(t) = (0.0570~m/s^3)~t^2$ (b) The squirrel is 3.31 meters from the initial position. (c) The magnitude of the velocity is 1.57 m/s and the direction is an angle of $65.9^{\circ}$ above the positive x-axis.

Work Step by Step

(a) $x(t) = (0.280~m/s)~t+ (0.0360~m/s^2)~t^2$ $v_x(t) = \frac{dx}{dt} = (0.280~m/s)+ (0.0720~m/s^2)~t$ $y(t) = (0.0190~m/s^3)~t^3$ $v_y(t) = \frac{dy}{dt} = (0.0570~m/s^3)~t^2$ (b) When t = 0, the squirrel is at the origin. At $t = 5.00~s$: $x = (0.280~m/s)(5.00~s)+ (0.0360~m/s^2)(5.00~s)^2$ $x = 2.30~m$ $y = (0.0190~m/s^3)(5.00~s)^3$ $y =2.38 ~m$ We can find the distance $d$ from the origin. $d = \sqrt{x^2+y^2}$ $d = \sqrt{(2.30~m)^2+(2.38~m)^2}$ $d = 3.31~m$ The squirrel is 3.31 meters from the initial position. (c) At $t = 5.00~s$: $v_x = (0.280~m/s)+ (0.0720~m/s^2)(5.00~s)$ $v_x = 0.640~m/s$ $v_y = (0.0570~m/s^3)(5.00~s)^2$ $v_y =1.43 ~m/s$ We can find the magnitude of the velocity. $v = \sqrt{v_x^2+v_y^2}$ $v = \sqrt{(0.640~m/s)^2+(1.43~m/s)^2}$ $v = 1.57~m/s$ We can find the angle above the positive x-axis. $tan(\theta) = \frac{1.43}{0.640}$ $\theta = tan^{-1}(\frac{1.43}{0.64}) = 65.9^{\circ}$ The magnitude of the velocity is 1.57 m/s and the direction is an angle of $65.9^{\circ}$ above the positive x-axis.
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