Answer:
D is the answer hope you it helps you
Answer:

Explanation:
In this case we have to use the Principle of conservation of Momentum:
<em>This principle says that in a system the total momentum is constant if no external forces act in the system. The formula is:</em>

<em>Where:</em>
Mass of the first object.
Mass of the second object.
Initial velocity of the first object.
Initial velocity of the second object.
Final velocity of the first object.
Final velocity of the second object.
In <u>this problem</u> we have:


Observation:
Is because the system has the same initial velocity.
First we have to find
,

We can rewrite it as:

Replacing with the data:

We found the final velocity of the cart, but the problem asks for the resulting change in the cart speed, this means:

Then, the resulting change in the cart speed is:

Answer: Gravitational force
Explanation:
A non contact force can be described as a force applied to an object by another body that is not in direct contact with it.
For example, an object thrown upwards will return back due to the force of gravity acting on it. So, it means Gravitational force is acting on the body without necessarily being in contact with that body.