April 12 is the International Day of Human Space Flight, which commemorates the first human space flight on April 12, 1961. The launch of a spacecraft is fundamental to all space activity. As a rocket flies it loses mass, because most of its mass is fuel (pure hydrogen and oxygen) that provides the propulsive force.
This Demonstration shows the dynamics of an ideal rocket from launch time to measured burn-out time, based on Newton's laws and Tsiolkovsky's rocket equation. Specify the rocket parameters and launch with the trigger.
Launching a Rocket by Frederick Wu