Question

which statement accurately describes an unbalanced force?
three rows of cement blocks form a foundation for a house, and the house rests on this foundation.
the force of a house pressing down on its foundation of cement blocks is 3,000 n.
each cement block supports a 2 - n force, but when the foundation is built in a staggered pattern, it can support 2,000 n.
a 2 - n force presses down on the cement block at the same time as a 1.5 - n force presses up on the cement block.

Explanation:

An unbalanced force occurs when the net force acting on an object is not zero. In the case of a 2 - N force pressing down and a 1.5 - N force pressing up on the cement block, the net force is \(2 - 1.5=0.5\) N (downward). This means there is an unbalanced force. In the first option, the house resting on the foundation implies balanced forces (weight of house and normal force from foundation). The second option just states a single force (no information about opposing forces). The third option is about the capacity of the foundation (not about unbalanced forces acting on a single entity at a particular moment).

Answer:

A 2 - N force presses down on the cement block at the same time as a 1.5 - N force presses up on the cement block.