An example of an unbalanced force is A. a bridge. B. a roller coaster going down the first drop. C. a tug of war game in which no one wins. D. a car parked in a garage.

B

Explanation:

Any object will be acted on by a force, when that object is not moving (or has an acceleration equal to zero), then the forces acting on that object are considered to be balanced.

A: Is balanced, because a bridge has multiple structures in place that prevent it from being unbalanced, and falling over.

B: Is unbalanced, because during a roller coaster ride, the acceleration changes constantly. Hence, during its first drop, the roller coaster is being acted on by unbalanced forces.

C: Is balanced, because although there are two forces acting in opposite directions (the pulling from both sides), the overall net force is equal to zero.

D: Is balanced, because the car is not moving, and hence it will have zero acceleration.

car parked is balanced since it's not moving or anything. A bridge is also the same. It's like constant and balanced on both side. A tug of war game where nobody wins is like it's balanced between the two teams and nobody wins. Only a roller coaster going down is not balanced since it's moving downward as a result of not being balanced. Answer is b