Why Buzz Lightyear’s rocket launch looks better than reality


The figure shows that the vertical position of the rocket increases by an (almost) constant amount from one frame to the next. In physics, we call it “constant speed”. Since this is a graph of position versus time, the slope of the line will be equal to this constant vertical velocity. As can be seen from the above figure, the launch speed of the rocket is 192 meters per second (m/s). This is too fast-but is this speed enough to actually reach space? The answer is yes and no. why is that.

Let me briefly introduce the escape velocity. Suppose you pick up an apple and throw it into the air at a speed of 10 meters per second. (This is quite fast for Apple.) As Apple moves up, it will slow down. Eventually, due to gravity, it will stop and then begin to fall towards the earth.

But suppose Apple is moving very fast, at 11.186 kilometer Every second. Then it will become high enough that gravity is not enough to stop it. That apple will run away.

Buzz Lightyear’s rocket is fast – but not so fast. Remember, we calculated it to move at a speed of 192 meters per second.But this is not a problem, because you don’t need to worry about escape speed If you have a rocketThe engine will continue to push the spacecraft to overcome this pulling force and keep it moving at a constant speed, so it will not fall back to the earth.

In the case of Buzz’s rocket, there are basically three forces interacting in this part of the motion. First, it is the thrust from the engine. Traditional chemical engines burn propellant to produce exhaust gas. All forces are in pairs, so when exhaust is expelled from the engine, it will propel the rocket in the opposite direction. (The advantage of rocket engines is that they can work in the Earth’s atmosphere and in airless space.)

The other two forces on the spacecraft are the downward traction caused by the interaction with the earth, and the air resistance in the opposite direction to the ship. Air resistance is caused by the collision of the rocket with the air.

As the spacecraft leaves the ground, both of these forces will eventually become insignificant. That’s because the further away from the center of the earth, the less gravitational force pulling the ship. Once the rocket flies out of the atmosphere, there is no more air resistance because there is no more air. The only power left will be the thrust from the engine, so the speed of the spacecraft should increase.

But… the real rocket does not work like this.Generally, the thrust produced by a rocket engine is Bigger More than gravitation.This means that the rocket going upward will accelerate It’s not just traveling at a constant speed.



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