Final answer:
An object experiencing zero net force means it has a balanced forces, hence no acceleration. This is true in the scenario with a balloon rising at a constant velocity, as the forces acting on it (gravity and buoyancy) are equal and opposite, resulting in zero net force. Hence, the scenario that describes an object experiencing zero net force is B) A balloon floating upward at a constant velocity.
Step-by-step explanation:
If an object is moving at a constant velocity, this indicates that is it experiencing no acceleration and hence no net force. The forces acting upon the balloon, gravity pulling it downwards and the buoyant force pushing it upwards, are balanced leading to a net force of zero. Unlike the other scenarios listed, where forces are unbalanced (causing acceleration), the blob retains a constant velocity because the forces acting on it are equal in magnitude but opposite in direction, hence resulting in a zero net force.
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