Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 7 - Impulse and Momentum - Problems - Page 196: 68

Answer

i) It is possible. ii) They do not necessarily have the same kinetic energy. - Object A: $p=12kg.m/s$ and $KE=36J$ - Object B: $p=12kg.m/s$ and $KE=12J$

Work Step by Step

i) We have $p=mv$, so even though 2 objects have different speeds, if they have appropriate masses, their momenta can still have the same amplitude. ii) We have $p=mv$ and $KE=\frac{1}{2}mv^2=\frac{1}{2}pv$ So if we have 2 objects A and B, where $p_A=p_B$ but $v_A\ne v_B$, then $\frac{1}{2}p_Av_A\ne\frac{1}{2}p_Bv_B$, or $KE_A\ne KE_B$ Therefore, 2 objects with the same momenta do not necessarily have the same kinetic energy. 1) Object A: $m=2kg$ and $v=6m/s$ $p_A=mv=12kg.m/s$ $KE_A=\frac{1}{2}mv^2=36J$ 2) Object B: $m=6kg$ and $v=2m/s$ $p_B=mv=12kg.m/s$ $KE_B=\frac{1}{2}mv^2=12J$
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