This graph shows that the vertical position of the rocket increases by a constant amount (approximately) from frame to frame. In physics, we call that “constant velocity”. Since this is a plot of land versus time, the slope of the line will be equal to this constant vertical velocity. From the above graph, you can see that the missile’s launch speed is 192 meters per second (m/s). That’s very fast – but is that speed enough to actually reach space? The answer is yes and no. Here’s why.
Let me give a brief overview of escape velocity. Suppose you take an apple and throw it into the air at 10 meters per second. (This is fairly fast for an apple.) As that apple moves up, it will slow down. Eventually, thanks to the force of gravity, it will stop and then begin to fall back toward the Earth.
But let’s say the apple is moving very fast at 11.186 kilometers per second. Then it rises high enough that the force of gravity is not strong enough to stop it. That apple will slip away.
The Buzz Lightyear missile is fast — but not that fast. Remember, we calculated that it was moving at 192 meters per second. But this is not a problem, because there is no need to worry about the escape speed If you have a missile. The engine will continue to propel the spaceship to overcome this tension and keep it moving at a constant speed, until it does not return to Earth.
In the case of the Buzz rocket, there are essentially three force interactions during this portion of the motion. First, there is the thrust from the engines. A conventional chemical engine burns fuel to produce exhaust gases. All forces come in pairs, so when the exhaust comes out of the engine, it pushes the rocket in the opposite direction. (The nice thing about rocket engines is that they work both in Earth’s atmosphere and in space, where there is no air.)
The other two forces on the spacecraft are the gravitational force pulling downwards due to its interaction with the Earth, and the air resistance force pushing in the opposite direction to the ship. Air resistance is caused by collisions between a missile and air.
When the spacecraft leaves Earth, these two forces will eventually become insignificantly small. That’s because moving away from the center of the Earth means that the force of gravity pulling on the ship decreases. Once the missile goes through the atmosphere, there will be no air resistance, because there will be no air. The only power left will be thrust from the engines, so the speed of the spaceship must be increased.
But… that’s not how real rockets work. Usually, a rocket motor produces a thrust that is Larger from the force of gravity. This means that a missile traveling upward will do so acceleration And not just traveling at a constant speed.