Edit: I didn’t understand how a jet engine worked, but now that I do, the question has been amended to this…
“Why does a rocket have to travel faster and faster the higher up it goes? Shouldn’t it require less and less speed as it is further from the earth it gets because there is a non-zero number(very small) of negative gravity change the higher you are?”
Edit #2: I think I suck at asking this so I’ll ask it like a 5 year old.
We have all seen videos of rockets taking off. They start very slowly, and then build in speed. Although, at first, they build up in speed. It’s not as if they torque off the earth at 20,000mph, although that would be ASTOUNDING to see. So here’s my super drawn out really dumb question that I cannot wrap my head around the answer for the life of me.
Let’s say you have a rocket going 100mph going 90 degrees straight up from the surface of the earth. Why can’t it just keep going 100mph straight up. Just keep going and going. Up, straight up. Up up up and away? Why can it move up starting from zero miles an hour? If it can move up at 5mph even for an instant, why can’t it continue at that velocity all the way up.
All the answers have been wonderful if I was asking how to get something in orbit. I’m asking why 100mph 90 degrees going straight up works down here, but not up there? I cannot find a straight answer to this question no matter what I google. I appear to be bad at research or this is just a stupid ass question. I really just don’t understand the physics of this at all.
Let’s try this another way. Say I threw a magic baseball that whatever velocity it was tossed at, it maintained until it hit a object. It doesn’t disregard gravity. It just has a magic anaerobic motor that maintains the speed. Like cruise control. Say I throw it 90 degrees straight up at 35mph. Will it leave Earth? Why or why not?
In: Engineering
I’m pretty sure this is a physics question about forces on an object. Think about an object on ice, the smoothest ice you can imagine (The main idea is to lower the friction on the item). If you were to give the hockey puck a single push, you would expect it to glide at a steady speed across the ice. This is the same concept as “An object in motion will stay in motion”. Without any other action on this hockey puck you expect it to maintain speed.
Now push on the hockey puck to get it going, but then give it a second additional push. It should now be going faster than the first hockey puck since it was given more force. This leads to the idea that each “piece of force” you add gives the puck more speed.
Now we want to get to a constant force. This is a little harder to imagine, but imagine you could keep pushing the hockey puck once per second. Each second you now keep adding more force which creates more speed. Each second the hockey puck will travel faster and faster because you give it an additional push.
This is what is happening in the rocket example. The rocket is creating the same amount of thrust (force) every second, so the first second the rocket has very very little speed because most of the thrust is working against gravity. Maybe 90% of thrust is just counteracting gravity, but that last 10% of thrust works like the pushes on the hockey puck. So each second 10% of the thrust adds more and more speed to the rocket.
Now onto your question roughly. So yes you could create a rocket that would maintain the same speed to get to space, and what this would mean is each push on the rocket would need less and less force behind it, but that would most likely be inefficient in either a fuel aspect or the engine thrust aspect. (This is the part I know least about)
Latest Answers