Fundamentals of Physics Extended (10th Edition)

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

Chapter 11 - Rolling, Torque, and Angular Momentum - Problems - Page 321: 16

Answer

$\beta = 0.4$

Work Step by Step

We can find the time it takes the object to fall $h = 0.10~m$: $h = \frac{1}{2}at^2$ $t = \sqrt{\frac{2h}{a}}$ $t = \sqrt{\frac{(2)(0.10~m)}{9.8~m/s^2}}$ $t = 0.14286~s$ We can find the required horizontal speed $v$ in order for the object to travel a horizontal distance of $0.506~m$ in this time: $x = v~t$ $v = \frac{x}{t}$ $v = \frac{0.506~m}{0.14286~s}$ $v = 3.542~m/s$ The rotational inertia of the object is $I = \beta MR^2$ We can find a general expression for the total kinetic energy: $K = \frac{1}{2}Mv^2+\frac{1}{2}I\omega^2$ $K = \frac{1}{2}Mv^2+\frac{1}{2}(\beta MR^2)(\frac{v}{R})^2$ $K = \frac{1}{2}Mv^2+\frac{\beta}{2}Mv^2$ $K = \frac{\beta +1}{2}Mv^2$ The gravitational potential energy at height $H$ is equal to the total kinetic energy just before rolling off the ramp. We can use conservation of energy to find $\beta$: $K_2+U_2 = K_1+U_1$ $K_2+0 = 0+U_1$ $\frac{\beta +1}{2}Mv^2 = MgH$ $\beta +1 = \frac{2gH}{v^2}$ $\beta = \frac{2gH}{v^2}-1$ $\beta = \frac{(2)(9.8~m/s^2)(0.90~m)}{(3.542~m/s)^2}-1$ $\beta = 0.4$
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