Students are using the experimental setup shown in the image in which the two ends of a string are attached to a car and to a hanger. The students conduct three trials in which they place metal discs on the hanger to manipulate the force applied to the car. As a result, the car accelerates along the table while two probes collect motion data. On the fourth trial of this experiment, a student places some discs on the car by mistake. In 1-2 sentences, explain how this would this change the acceleration or velocity???

Placing discs on the car would increase its mass, resulting in a decrease in acceleration and possibly a decrease in velocity as well, depending on the strength of the force applied by the car's engine.