XPost: alt.astronomy, sci.military.naval, soc.history.war.misc
XPost: alt.fan.heinlein
Kualinar wrote:
Le 2024-05-14 à 19:56, bertietaylor a écrit :
Kualinar wrote:
Le 2024-05-13 à 03:08, bertietaylor a écrit :
R Kym Horsell wrote:
In alt.astronomy bertietaylor <[email protected]> wrote:
Kualinar wrote:
Le 2024-05-12 ?? 20:04, bertietaylor a ??crit??:
They never went there.
bt
Are you a flatard or one of those stupid Moon landing denier ?
Am a ghostly cyberdog that cannot think why they did not jump up
ten feet.
- typically unconvincing bs snipped -
bt
Your calculations are wrong.
The avg astronaught weighs around 110 lb.
Which is 110/7 = say 16 lbs on the moon.
The moon suit weighs 180 lb.
Which is 180/7 = say 27 lbs on the moon.
Total weight on moon = 16+27= 43 lb
If a 110 lb man can jump up 1 foot up on earth,
then with same strength a 43 lb man can jump up 2 feet up on Earth.
And on the Moon, the 43 lb man can jump up 2*7= 14 feet up.
Now 14>10, so my question remains.
However if 110lb man carries a 180lb load on his back, on Earth, he
would have to lean forward as he does.
Of course, if we are filming it on the desert in Nevada, the 180lb
pack could be but say 30 lb.
Why my scepticism? Actually it was disappointment. In the early 60s
I had got a present, a book about two American kids going to the
Moon. There was a picture of someone on the Moon jumping up 10-12
feet, and that was very impressive.
The kind of shuffling the astro-nots did was not satisfactory.
bt
The height is not 6x but 2x whatever they are tryng to do.
Astronaughts were traditionally anglo so jumping 5 ft would have
been a stretch anyway.
They could easily jump 10 feet on the Moon...
....when jumping in a pressurized gymnasium where they don't need to wear
a heavy and stiff space suit.
While the weight is one sixth of the weight on the Earth, the mass is
still the same. You need to accelerate the full mass.
To jump up 0.5 m for a 50 kg mass on Earth, the reaction from the soil
must be such as to overcome gravity and give extra acceleration.
using vv=uu+2as, with v final velocity as zero, u = sqrt of 2*g of
earth * height jumped or sqrt 2*9.8*0.5 = sqrt 9.8 = say 3 m/s.
To get that velocity, the force from the man jumping would be his mass
times acceleration over the time from 0 to 3m and that is say 0.1
second. So acc = 3/0.1 = 30 m/s/s and reaction upon Earth is 50 * 30 =
1500 newtons. With same force exerted on the Moon's surface, the man
would have an acceleration of 1500/50 = 30 m/s/s as on Earth.
Now if the surface is as hard as on Earth, like he is jumping of a rock,
then that acceleration time will be comparable say once again 0.1 sec.
Then as on Earth, he will get an upward velocitu of 3 m/s for the jump.
Again using vv=uu+2as with a=g/7 for the lunar scene and u=3 we get
h=uu/(2g/7)=63/20= say 3 m.
Why are you ignoring the mass of the space suit ?
energy = mgh (general formula) or h=energy/(mg)
height jumped on earth = energy/((mass of man and suit)*g)
height jumped on moon = energy/((mass of man and suit)*(g/6))
Dividing one by the other
height jumped on Earth/height jumped on Moon = (energy/((mass of man and suit)*g))/((mass of man and suit)*(g/6))
The mass and energy terms cancel out leaving us with
height jumped on Earth/height jumped on Moon = 1/6
You are assuming that the mass to accelerate on Earth and on the Moon is
the same. It is NOT the same.
Mass is ALWAYS same.
There is such a thing in physics as THE LAW OF CONSERVATION OF MASS.
The force exerted by the mass varies as the acceleration upon it.
Force = mass times acceleration, as per the second law of Newton.
On Earth, the acceleration is called g, or 9.8m/s/s or 32.2 feet/s/s
So with same force and similar launch surface the man can jump 6 times
higher, actually gearth/gmoon times.
Yes, the same force will accelerate the SAME mass. But, here, the mass
is NOT the same.
Mass of a body is exactly the same. All over the universe!
The space suit is heavy, meaning that the initial
velocity get reduced.
The question is that he is wearing the same heavy suit on the Earth.
If with that suit he can jump 6 inches on Earth, on Moon he will jump 36 inches or three feet with that same suit.
The space suit is also stiff, limiting the
duration of the acceleration and the available accelerating force.
LESS force for LESS time = SMALLER initial velocity.
Does not matter how stiff that is. If he can jump 6 inches on Earth with that suit, from a similar jump surface he can jump 3 feet on the Moon. Plenty of rocks on the Moon; apparently, they brought back a few! Well, in that case standing on such rocks
he would get the same reaction from the surface as on Earth.
Instead, there was shuffling, probably helped with wires on cranes to give some sense of unreality. Not a single attempt to jump, even. Or throwing a rock up and showing it coming down slowly. Or picking up the lunar dust and show it falling down slowly.
What we have are fluttering flags, weird uneven shadows, no stars, photo negatives mysteriously lost, very clear photos with clumsy gloves, very deep footprints (now that is a giveaway!). Also see how they are bending forward with the weight. Used to
weighing 110 lb on earth, even with suit on they would weigh (110+180)/6 = 290/6 = say 50 lb or half their earth-weight. They should have an upright posture, feeling very light, not weighed down.
But as this was filmed on Earth, even with a non 180lb backpack, they did look so stiff and heavy.
Hollywood tricks, one showing like the famous C rock used as prop.
Exactly as told in the early 1960s space literature for kids.
That literature completely neglected to take the mass of the space suit
into consideration.
Or they took for consideration a very light suit, not 180lb but say 60 lb.
If you have a 60lb suit and have mass 110 lb, you can jump up with energy 600joules
h = 600/(77.27*9.8/6) = 4.75 meters or 15 feet and 5 inches.
Exactly as per the children's literature book of the late 50s- early 60s.
Well in those days they certainly knew their physics. They were not confused by all the relativity stuff!
bt
With your Earth weight estimate, that's 132Kg of mass to accelerate.
Okay.
That 132Kg is still 132Kg on the Moon's surface.
Certainly.
The weight is lower,
Yes.
going from 1294 Newton down to 216 Newton,
Great.
but, the mass don't change.
Absolutely, mass never changes.
The mass limit the possible acceleration.
Acceleration due to gravity is 1/6 there, so with same energy the man jumps 6 times higher.
h = energy/(mass * gravitational acceleration)
The duration of the
acceleration also don't change.
That is an assumption. We assume it is the same sort of hard surface whether on Earth or Moon. As the Moon is rocky this is a valid assumption. Now if you are in a swampy land on Earth you cannot jump too much can you.
Then, there is a consideration of safety. Jumping that 3.3m is pretty,
and uselessly, risky when you are in a big space suit that limit your
movements and the closest medical facility is some 250 000 Km away.
O dear us. These brave people are hopping off Earth on a pillar of fire, going into deep dark space, coming down at horribly high speeds, knowing they could be killed at any moment by a meteor, braving radiation with unknown effects... and they will be
scared of jumping a little bit on the Moon, just to show off and enjoy themselves?
We dogs don't buy that.
bt (Arindam's ghostly cyberdogs and his best friends)
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