Question

which statement accurately describes a balanced force?
a marble resting on the sidewalk suddenly begins to roll downhill without being touched.
a 25 - n force acts on the left side of the marble at the same time as a 25 - n force acts on the right side of the marble.
a 2 - n force presses down on the marble at the same time as a 1.5 - n force presses up on the marble.
a marble rolling downhill suddenly comes to rest at a garden wall.

Explanation:

Balanced forces are equal in magnitude and opposite in direction, resulting in no net force.

• Option A: A marble starts moving without being touched implies an unbalanced force (gravity acting alone initially, but the description is about sudden movement without prior balanced state).
• Option B: A 25 - N force on the left and 25 - N force on the right. Since the forces are equal in magnitude ($F_1 = F_2=25\ N$) and opposite in direction (left and right), the net force $F_{net}=F_1+( - F_2)=25 - 25=0\ N$. This is a balanced force situation.
• Option C: A 2 - N downward force and 1.5 - N upward force. The net force $F_{net}=2 - 1.5 = 0.5\ N$ (downward). These are unbalanced forces.
• Option D: A marble rolling downhill (has an initial force, likely gravity - related unbalanced force causing motion) and then coming to rest (a new unbalanced force, the normal force from the wall and friction acting against the motion).

Answer:

B. A 25 - N force acts on the left side of the marble at the same time as a 25 - N force acts on the right side of the marble.