The equation
(option 3) represents the horizontal momentum of a 15 kg lab cart moving with a constant velocity, v, and that continues moving after a 2 kg object is dropped into it.
The horizontal momentum is given by:


Where:
- m₁: is the mass of the lab cart = 15 kg
- m₂: is the <em>mass </em>of the object dropped = 2 kg
: is the initial velocity of the<em> lab cart </em>
: is the <em>initial velocit</em>y of the <em>object </em>= 0 (it is dropped)
: is the final velocity of the<em> lab cart </em>
: is the <em>final velocity</em> of the <em>object </em>
Then, the horizontal momentum is:

When the object is dropped into the lab cart, the final velocity of the lab cart and the object <u>will be the same</u>, so:

Therefore, the equation
represents the horizontal momentum (option 3).
Learn more about linear momentum here:
I hope it helps you!
The point of the orbit closest to Earth<span> is called perigee, while the point farthest from </span>Earth<span> is known as apogee</span>
Acceleration........................................
Personally, I agree with your answer, namely that the likely-intended event happening here is one of acceleration. Having said that, I also want to add: it pains me to see this type of wording because, clearly, it is vague and only invites confusion of the type you are talking about.
Good luck!
To solve this problem we will apply the concepts related to gravitational potential energy.
This can be defined as the product between mass, gravity and body height.
Mathematically it can be expressed as


Therefore the change in the internal energy of the system is 255.78