Answer:
D. The cart is moving at a constant speed or velocity
Explanation:
Equilibrium is a state of body in which it is either at rest or moves with uniform velocity. The sum of forces acting on such a body is always zero and the sum of all the torques acting on it is also zero.
There are two types of equilibrium as follows:
Static Equilibrium: When a body is at rest it is said to be in static equilibrium.
Dynamic Equilibrium: When a body is moving with constant velocity, then it is said to be in dynamic equilibrium.
Hence, the correct option here will be:
<u>D. The cart is moving at a constant speed or velocity</u>
