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!
Force=mass x acceleration
f= 0.5 x40
f=20N
The new acceleration is 
Explanation:
We can answer this problem by applying Newton's second law, which states that:

where
F is the net force on an object
m is the mass of the object
a is its acceleration
The equation can be rewritten as

In this problem, the initial acceleration is

Later:
- The net force is tripled: 
- The mass is halved: 
Therefore, the new acceleration is:

which means that the new acceleration is 6 times the original acceleration, therefore

Learn more about acceleration:
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Correct answer is letter B. sandstone