Physics (10th Edition)

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

Chapter 7 - Impulse and Momentum - Check Your Understanding - Page 177: 4

Answer

a) not possible b) possible

Work Step by Step

a) We have $p=mv$ and $KE=\frac{1}{2}mv^2$ For $p$ to be zero, either $m=0$ or $v=0$. Either of these cases, however, will make $KE$ zero, too. Therefore, it is not possible for an object to have a kinetic energy but no momentum. b) Consider 2 objects A and B: $\vec{p}_A=m_A\vec{v}_A$ and $\vec{p}_B=m_B\vec{v}_B$ These 2 objects have total momentum $\sum \vec{p}=\vec{p}_A+\vec{p}_B=0$, which makes their magnitudes $p_A=p_B=p$ Now let's look at their kinetic energies: $KE_A=\frac{1}{2}m_Av_A^2=\frac{1}{2}pv_A$ and $KE_B=\frac{1}{2}m_Bv_B^2=\frac{1}{2}pv_B$ $\sum KE=\frac{1}{2}p(v_A+v_B)\gt0$ because $p, v_A, v_B$ all are greater than 0 So it is possible to have a nonzero total kinetic energy.
Update this answer!

You can help us out by revising, improving and updating this answer.

Update this answer

After you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.