To solve this, we must first determine the net force acting on the object. Since the forces given are in opposite directions, we subtract them: 35 newtons (southward) - 25 newtons (northward) equals 10 newtons (southward). This is our net force. Next, we apply Newton's Second Law of Motion, which states: force equals mass times acceleration (F = m*a). If we rearrange that formula to solve for acceleration, we get acceleration equals force divided by mass (a = F/m). Plugging in our values, we find that the magnitude of the object's acceleration is 10 newtons divided by 15 kilograms, which equals 0.67 meters per second squared (southward).