In scientific notation, "E" represents the exponent in powers of ten, such as 1.20E+7, which means 1.20 times 10 to the power of 7. The discussion revolves around calculating the acceleration and time required for a freight train to reach a certain speed, emphasizing the importance of converting units correctly, such as from km/h to m/s. Participants also explore the forces acting on a bullet fired from a rifle, confirming that initial velocity is zero when calculating acceleration. Additionally, the tension in ropes supporting blocks in an accelerating elevator is analyzed, highlighting the need to consider both the tension and gravitational forces in calculations. Overall, the thread illustrates the application of fundamental physics principles in solving problems involving forces and motion.