<div>
In physics, the kinetic energy of an object is the energy that it possesses due to its motion.[1] It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.<br />
<a href="https://en.wikipedia.org/wiki/Kinetic_energy" rel="ugc">https://en.wikipedia.org/wiki/Kinetic_energy</a><br />
System is not a physical object <a href="https://filedb.experts-exchange.com/incoming/2018/09_w36/1382007/2018-09-07_16-28-43.png" target="_blank" title="2018-09-07_16-28-43.png (209 KB)"><img alt="2018-09-07_16-28-43.png" class="file-block lazyload" style="max-width: 800px;" data-src="https://filedb.experts-exchange.com/incoming/2018/09_w36/800_1382007/2018-09-07_16-28-43.png" /></a>
</div>


In physics, the kinetic energy of an object is the energy that it possesses due to its motion.[1] It is defined as the work needed to accelerate a body of a given mass from rest to its stated velocity. Having gained this energy during its acceleration, the body maintains this kinetic energy unless its speed changes. The same amount of work is done by the body when decelerating from its current speed to a state of rest.
https://en.wikipedia.org/wiki/Kinetic_energy [https://en.wikipedia.org/wiki/Kinetic_energy]
System is not a physical object 2018-09-07_16-28-43.pnghttps://filedb.experts-exchange.com/incoming/2018/09_w36/1382007/2018-09-07_16-28-43.png

2018-09-07_16-28-43.png

<div>
Is System 2 isolated system ?
</div>


naseeam

<div>
<div class="content wysiwyg-content">
The question is from Physics book titled &quot;Physics for Scientists and Engineers&quot; by Randall D. Knight. &nbsp;Attached is part of chapter 10.1.<br />
<br />
&quot;Objects A and B are oblivious to our choice of system, so change in total kinetic energy for system 2 is exactly the same as for system 1.&quot;<br />
<br />
How is that possible? &nbsp;System 1 has kinetic energy because there are external forces but System 2 doesn't have external forces.<br />
<a href="https://filedb.experts-exchange.com/incoming/2018/09_w36/1381996/interactive_system.PNG" target="_blank" class="file-inline" title="Potential_Energy (179 KB)"><svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512"><path d="M67.508 468.467c-58.005-58.013-58.016-151.92 0-209.943l225.011-225.04c44.643-44.645 117.279-44.645 161.92 0 44.743 44.749 44.753 117.186 0 161.944l-189.465 189.49c-31.41 31.413-82.518 31.412-113.926.001-31.479-31.482-31.49-82.453 0-113.944L311.51 110.491c4.687-4.687 12.286-4.687 16.972 0l16.967 16.971c4.685 4.686 4.685 12.283 0 16.969L184.983 304.917c-12.724 12.724-12.73 33.328 0 46.058 12.696 12.697 33.356 12.699 46.054-.001l189.465-189.489c25.987-25.989 25.994-68.06.001-94.056-25.931-25.934-68.119-25.932-94.049 0l-225.01 225.039c-39.249 39.252-39.258 102.795-.001 142.057 39.285 39.29 102.885 39.287 142.162-.028A739446.174 739446.174 0 0 1 439.497 238.49c4.686-4.687 12.282-4.684 16.969.004l16.967 16.971c4.685 4.686 4.689 12.279.004 16.965a755654.128 755654.128 0 0 0-195.881 195.996c-58.034 58.092-152.004 58.093-210.048.041z"/></svg>interactive_system.PNG</a>
</div>
</div>


interactive_system.PNG

The question is from Physics book titled "Physics for Scientists and Engineers" by Randall D. Knight.  Attached is part of chapter 10.1.

"Objects A and B are oblivious to our choice of system, so change in total kinetic energy for system 2 is exactly the same as for system 1."

How is that possible?  System 1 has kinetic energy because there are external forces but System 2 doesn't have external forces.

Why change in total kinetic energy is same for Two different systems ?

The Math / Science topic primarily includes discussions of mathematics, physics, statistics and economic analysis, but also biology, chemistry and other sciences.