how can we be wieghtless in a spacecraft that is still under a planets gravitational pull?

Question

The earth and the beyond and also the whole universe

Answer 1

THE CRAFT IS KEEP OUT OF THE PLANET'S PULL , IF IT WENT ROUND A PLANT , SAY , 20 TIME'S IT WOULD BE PULLED DOWN THAT IS WHY

Answer 2

This all depends on the size of the object.
The earth doesnt have alot of gavitational pull, so we can break free of this. Whilst under the gravitational pull, we are never fully weightless, only partially.
Once free of this, we become weightless.
The gravitational pull of the sun on the earth is far larger than the pull of the earth on a spacecraft. If we were to take the spacecraft off from the sun, it would be extremely hard and would take a longer amount of time for the people on board to become weightless. (Even if they were dead from the heat)
toodles... xx

Answer 3

Technically speaking astronauts are not weightless when they are in orbit, they are in freefall. The spacecraft is actually 'falling' at the same rate as the astronaut is falling so they appear to be weightless.

There is an airplane they call the 'Vomit-Comet' because it flies in a parabola shape. On the downward slope of the parabola, the plane is 'falling' at the same rate as the people on board so they appear to be weightless as well. This is how they train astronauts to deal with 'weightlessness' and it is also how they filmed much of the movie Apollo 13 to simulate zero-gravity.

Answer 4

Yes a common example experiment is that of a descending lift or elevator.

Our perception of weight is simply due to the Earths surface pushing back up at us as gravity tries to pull us down.

When we are in a lift going down, the floor is moving downward away from us - i.e. in the same direction as gravity is pulling us. This reduces the effect of gravity and hence we feel lighter.

If the lift was travelling down at the same rate as gravity is pulling us, then the lift would cancel out the effect of gravity and hence we would have the illusion of weightlessness.

Answer 5

The centrepital force pushing *out* on the spacecraft and the astronauts inside balances with the pull of gravity *in*, so it feels like weightlessness.

Centrepital force is realized when an object has angular acceleration. Velocity is speed and direction. Acceleration is a change in velocity, so if the speed remains constant, and the direction changes (circular orbit), you still have acceleration (angular acceleration). F = m*a 'a' is the angular acceleration, therefore there is Force, called centrepital force.

.

Answer 6

It is a common misconception that when you go into space, you experience "zero-gravity". Zero-gravity is just a cute name someone came up with. In theory, every bit of matter in the universe affects you gravitationally. In practice, the vast majority of it is simply negligible.

When you are on the ground, you have two things going for you that keep your feet on the ground. One is air pressure. Right now, you have approximately 14.7 pounds per square inch sitting on top of you. Another thing is the atmosphere, which acts as a sort of roof, to keep you from flying away.

When astronauts take space-walks, they are experiencing suspended free-fall. That is, the forces in space pushing them around are equal or greater than the gravitational pull of the Earth.

I hope that answers your question.

Answer 7

If the spacecraft is in orbit, moving around the earth without using its engines, then there will be no gravity inside the craft because objects in free-fall are wieghtless. (Being in orbit is being in free-fall).

This realization is from EInstein. When you are in free-fall your downward acceleration cancels out gravity.

Answer 8

First, with reference to my response to the other instance of this question ;
Phil2 – ok, you are correct about lifting the arm, that is related to mass and not weight, so that was cheating. Experience is still valid as a rock wouldn’t ask the question, but more importantly the question really relates to frames of reference – ie. why is the inside of a spacecraft an inertial frame of reference ?
Bottom line is this question can be answered definitively using classical physics (Newton and Galileo), Einstein is only required if you wish to take the question to further depths on the nature of gravity.
So, I assure you, the following IS the answer, in terms of a tennis ball (a kind of soft rock).

On a train
1) Roll a tennis ball off the table and it follows a curved path to the floor. We attribute this result to the weight of the ball, under the influence of gravity

On a spacecraft in orbit
1) A spacecraft in orbit is in free fall (see other responses below, eg. my first one, JasonT)
2) All objects fall at the same rate under the influence of gravity (Galileo), so in free fall everything in the spacecraft is falling at the same rate; you, the tennis ball, the table, the floor
3) Roll the ball off the table and it will follow a straight line parallel to the plane of the table top, in constant motion (Isaac Newton – first law of motion) – It doesn’t fall to the floor, so it must be weightless ???
4) In truth when the ball rolls off the table it does fall, just as the ball did on the train. However in the spacecraft, everything else is also falling at the same rate. As the table, floor and ball are all falling at the same rate, the ball appears to follow a straight line, and doesn’t move to the floor. This is all about perspective (or experience), as described in bullets 5 and 6 below.
5) Observer in the spacecraft – The ball rolls off the table and continues in a straight line. We are all weightless, and existing in an inertial frame of reference
6) Observer on the ground (with a big telescope, looking inside the spacecraft) – The ball rolls off the table and falls, following exactly the same curved trajectory as that which rolled off the table on the train. However, as described in bullet 4, the whole spacecraft is also falling so the ball never reaches the floor and continues on a path parallel to the plane of the table top

Hope this is a clear explanation. You are not weightless in the spacecraft, however the laws governing your motion inside, and with reference to, the spacecraft are not influenced by your weight, but purely by Newton’s Laws of Motion;
"An object at rest will remain at rest unless acted upon by an external and unbalanced force. An object in motion will remain in motion unless acted upon by an external and unbalanced force" - Newton
See
1) http://en.wikipedia.org/wiki/Newton%27s_laws_of_motion
2) http://en.wikipedia.org/wiki/Inertial_fram

Pretzels – you will be interested to note that the second reference refers to the fictitious nature of your centrifugal force. That is why your answer is incorrect

Answer 9

You have the impression of being weightless when you are falling at the same speed as the vessel you are in.

A similar phenomena can be attained in airplanes. They fly high, then drop quickly towards the earth. The people inside them appear to float.

Answer 10

NO - PhilipB, it is the acceleration in a lift that will affect your weight, not its speed.

Nothing travels at the same RATE as gravity - you may have an acceleration equal to (the acceleration due to) gravity.