Question

in which situation is the object experiencing unbalanced forces?
a a box resting on a horizontal floor.
b a car slowing as it reaches a traffic light.
c a car with its cruise control set to 30 km/h.
d a penny at terminal velocity after falling off of a building.

Explanation:

To determine when an object experiences unbalanced forces, we use the concept that unbalanced forces cause a change in motion (acceleration, deceleration, or change in direction).

• Option A: A box at rest has balanced forces (gravity and normal force cancel).
• Option B: A car slowing down is decelerating, meaning there's a net force (unbalanced) acting to reduce its speed.
• Option C: A car with cruise control at constant speed has balanced forces (no acceleration).
• Option D: A penny at terminal velocity has balanced forces (gravity and air resistance cancel, constant speed).

So the car slowing (Option B) has unbalanced forces.

Answer:

B. A car slowing as it reaches a traffic light.