In the scenario, four individuals each weighing 100 kg are holding a 1200 kg balloon, and when three let go, the balloon accelerates upward at 2 m/s². To determine the tension in the rope held by the last person, Newton's second law is applied, considering both the gravitational force and the tension. The total force acting on the person is the difference between the tension and their weight, leading to the equation T - mg = ma. A diagram illustrating the forces can clarify the relationship between tension, weight, and acceleration. Understanding these dynamics is crucial for accurately calculating the tension in the rope.