Which term describes forces that produce a net effect on motion when an object accelerates or changes velocity?

• A. Mass
• B. Unbalanced forces
• C. Air Resistance
• D. Velocity

Answer: (B)

When objects change their motion, it’s because there is a net force acting on them. The total effect of all the forces — their sum, with direction taken into account — determines whether the motion changes. If all forces balance out, the net force is zero and the object maintains its current velocity. If the forces don’t balance, there is a net force that causes acceleration in the direction of that net force. That condition is described by unbalanced forces.

So, unbalanced forces are the forces that produce a net effect on motion when an object accelerates or changes velocity. Mass and velocity are properties of the object and its motion, and air resistance is one force that can contribute to the net force, but the general term for the situation that leads to a change in motion is unbalanced forces.