Final answer:
The unbalanced force on a car that is coming to a stop from a speed of 25 m/s will be negative, opposite to the direction of motion. This is due to the requirement of a deceleration force to reduce the car's speed to zero.
Step-by-step explanation:
When a car that is moving at a speed of 25 m/s comes to a stop, the unbalanced force on the car while stopping will be negative. This is because the force required to stop the car must be applied in the opposite direction to the car's motion. According to Newton's second law of motion, the object will decelerate when a force is applied in the opposite direction of its velocity, indicating a negative acceleration.
Since the car is decelerating, the acceleration is negative. If we look at the mathematical representation of the car's change in velocity, we find that a decrease in speed (from 25 m/s to 0 m/s) can be represented as a change in velocity which is negative. Consequently, the acceleration, which is the rate of change of velocity, is also negative. This negative acceleration aligns with the force being applied in the direction opposite to the motion of the car to bring it to a stop.