If there was no force (i.e. you are weightless) Newton s first law says you would travel in a straig

Most of our regular readers understand why astronauts and objects appear to float around on the International Space Station , but there are some misconceptions and preconceived notions out there on this topic that aren t true and don t represent a very good understanding of physics! This video provides an entertaining look at some of the ideas people have about the zero-gravity environment on board an orbiting spacecraft, and shows why the astronauts actually appear weightless.
The main thing to understand here is that there IS gravity in space. This is a very common misconception. What keeps the Moon in its orbit around the Earth? Gravity airline tickets from japan . What keeps the Earth in orbit about the Sun? Gravity . What holds galaxies together? Gravity .
If you built a tower on the Earth 370 km (230 miles) high, about as high as the Space Station s orbit, the gravity on top of the tower would be almost as strong as if you were on the ground. If you stepped off the top of the tower, you would drop to the Earth just as Felix Baumgartner will do later this year when he attempts to jump from the edge of space. (Of course, this does not account for the freezing temperatures airline tickets from japan that would ultimately cause your demise, or how no air or air pressure would kill you, or how dropping through the atmosphere would seriously do a number on your body parts. And then that sudden stop would be bad, too.)
The astronauts, the ISS itself and other objects in Earth orbit aren t floating, they are actually airline tickets from japan falling. But they don t fall to the Earth because of their huge orbital velocity. Instead, they fall around Earth. Objects in Earth orbit have to travel at least 28,160 km/h (17,500 mph). So, as they accelerate towards the Earth, the Earth curves away beneath them and they never get any closer. Since the astronauts have the same acceleration as the space station, they feel weightless.
There are times when we can be weightless briefly on Earth, when you are falling. Have you ever been on a roller coaster and just past the peak of a hill as the car starts to go down, your body lifts from the seat? If you were in elevator a hundred stories high, and the cable broke, as the elevator fell, you would float inside the elevator car. Of course, in that case the ending would be rather disastrous.
And also you ve probably heard about the Vomit Comet the KC 135 airplane that NASA uses to create short periods of weightlessness for astronaut training and to test out experiments or equipment in zero-G, as well as the commercial Zero-G flights where the plane flies in a parabola, airline tickets from japan and like a roller coaster (but at greater speeds airline tickets from japan and higher altitudes) when the plane goes over the top of the parabola and heads downward, a zero gravity environment is created as the plane falls. Luckily, the plane pulls out of the fall and levels off.
Let s go back to the tower. airline tickets from japan If instead of just stepping off the tower, you took a running leap, your forward energy would carry you away from the tower at the same time that gravity pulled you down. Instead of hitting the ground at the base of the tower, you would land a distance away. If you ran faster, you could jump further from the tower before you hit the ground. If you could run as fast as the space shuttle and ISS orbits the Earth, at 28,160 airline tickets from japan km/h (17,500 mph), the arc of your jump would make a circle around the Earth. You would be in orbit and weightless. You would be falling without hitting the ground. airline tickets from japan Spacesuit and ample breathable air needed, airline tickets from japan however.
The International Space Station, the space shuttle, and satellites are designed to stay in orbit, neither falling to the ground nor shooting off into space. They orbit the Earth about every 90 minutes.
Nancy Atkinson is Universe Today's Senior Editor. She also is the host of the NASA Lunar Science Institute podcast and works with the Astronomy Cast and 365 Days of Astronomy podcasts. Nancy is also a NASA/JPL Solar System Ambassador.
What s the situation when you re on the way to the moon ? For example the movie Apollo 13 did show us that the astronauts in the capsule were weightless on the way to moon. On this route they don t have any kind of orbital velocity. What s the explanation for their weightlessness in this situation ? (Or was the movie false ?)
It s still a kind of orbit, even though it s a somewhat extreme one, very eccentric, airline tickets from japan and you get captured by the Moon s gravity airline tickets from japan before you can complete it. Then, you are in another eccentric orbit around the Moon, until you fire your retros and enter a more conventional, less eccentric lunar orbit.
Of course, Apollo fired its engines once and then coasted to the Moon, allowing the astronauts to be weightless on the way, but if you were in some kind of craft that travelled under constant rocket power then you would feel this acceleration as weight.
I suppose that it s better to get to a speed just sufficiant not to fall too fast to the ground, so they can adjust airline tickets from japan the altitude, than too much velocity that could put the ISS far away and eventually quit the Earth s environment on a trip far away into space.
Not quite objects in orbit around a body won t spiral in toward that body, nor will they spiral out (except in the case where they exceed the escape velocity) without an external force acting upon them (i.e. atmospheric drag, or thrust)
Instead, they ll orbit in an ellipse. So as you said, the perigee is less than the apogee (by definition) but this is the nature of an elliptical orbit no thrust has to be applied to maintain this orbital path.
ACTUALLY YOU ARE WEIGHTLESS. YOU STILL HAVE MASS THOUGH. MASS PROVIDES NO FORCES airline tickets from japan EITHER. THE FORCE OF GRAVITY BETWEEN THE MASS OF THE EARTH AND YOUR BODY, AS WELL AS THE FORCE PROVIDED BY THE SHUTTLE PROVIDES THE FORCE.
You are confusing mass with weight. Weight is mass subjected to the acceleration of gravity. Newton s second law, force equals mass times acceleration (F = ma) , tells us that the force of gravity g = 9.8m/s^2 on a mass m gives a force F we call weight. So objects in orbit fall as the same rate of acceleration due to gravity have no mutual acceleration between themselves. This is the source of weightlessness.
You are the one who s confused. As you rightly state, F = ma, F is the weight, a is 9.8 m/s^2. Given those facts, a person with mass 70 kg weighs (70 * 9.8) Newtons, or a little less than 700 Newtons.
If there was no force (i.e. you are weightless) Newton s first law says you would travel in a straight line. To travel in a circular or elliptical path there must be a force and that force is your weight.
In a Newtonian frame everything on the spacecraft including you are falling at the same rate of acceleration. Therefore the absence of differential accelerations means everything is weightless. This means that being on a reference frame that is falling or in an orbit is indistinguishable from being on a frame far removed from gravity fields, say in interstellar space or way out between galaxies. In both cases if you are in a capsule and can't look out you can't perform an experiment to distinguish between the two. This is the basis for the equivalence principle Einstein invoked to work general relativity. airline tickets from japan It is then for this reason the force of gravity in Newtonian mechanics is really a pseudo-force. Gravity is not really a force in a strict sense, but is due to the motion airline tickets from japan of paths in space or spacetime, where if that is curved the paths are extremal curves in the space.
This works for the capsule or the spatial extent of the frame very small. Gravity in the Newtonian perspective has a radial dependency, and a capsule with some spatial extent will then have a tidal acceleration on it. This tidal force is physically real, while the standard Newtonian force of gravity can be "removed" as a pseudo-force. In general relativity the tidal force is due to a portion of the Riemann curvature, but the Newtonian force of gravity is due to the connection terms that can be removed by coordinate choice.
Looks like we are talking at cross-purposes. The statement I originally commented on was So, when you are in orbit, you are in free fall, and are weightless. This clearly establishes the reference frame as the body being orbited (i.e. Earth). You are talking about a different reference frame (the spacecraft).
With Earth as the reference frame, the astronaut and the spacecraft are both accelerating at 9.8 m/s^2 and each has a weight (in Newtons) equal to 9.8 times its mass (in kg), and this weight provides the centripetal force that keeps them in orbit.
In which case no matter where you are anywhere in the Universe you can never be weightless and the term becomes meaningless. The statement you are referring to explicitly equates being in free fall and being weightless, which therefore defines weight as the reaction airline tickets from japan force of something on the Earth s surface airline tickets from japan to your downward acceleration. This is intuitive as it allows your weight to change if, for example, you are in an accelerating lift (elevator) airline tickets from japan or aeroplane (airplane).
Let s do another problem and compute the weight of the Space Shuttle in low earth orbit. On the ground, the orbiter weighs about 250,000 pounds. In orbit, airline tickets from japan the shuttle airline tickets from japan is about 200 miles above the surface of the earth. As before, the gravitational constant ratio is the square of (4000/4200) which equals .9523*.9523 = .907. On orbit, the shuttle weighs 250,000 airline tickets from japan * .907 = 226,757 pounds. Notice: the weight is not zero. The shuttle is not weightless in orbit.