if your dropped a pound coin...

[spaced]

...from the top of the eiffel tower, would it pick up enough speed and weight to kill someone if it hit someone on the top of the head at the base?

[jake-the-peg]

Choose your weapon with more care! :c)

According to Dennis Thompson ([email protected]), safety testing at NASA's Zero Gravity Research Center in Cleveland concluded that coins falling from a height of 510' in air achieve a terminal velocity that is too low to seriously injure a person it strikes, much less bury itself in concrete. Other more aerodynamic objects, such as pens, can achieve a significantly higher velocity and can constitute a hazard to people below.

http://tafkac.org/science/penny_falling_impact .html />

[CT]

http://www.tafkac.org/science/penny_falling_im pact.html
The link before didn't work for me. Hopefully this one will.

[jake-the-peg]

Ah sorry

This always happens if you paste a link at the end of a post and don't press return after it you get a <p> at the end of the link just delete it and it'll work

[rojash]

It won't, of course, pick up any weight at all...

[bernardo]

It would increase in weight because it is getting closer to the centre of the Earth.

[LotusEater]

It wouldn't increase in weight because it was getting closer to the centre of the Earth.

[kempie]

Then why do astronauts become "weightless" when they travel away from the centre of the Earth?

Do not confuse weight with mass.

[KRUSTY]

Astronauts become 'weightless' only because of the lack of gravity in space - they still weigh the same! A coin dropped from the top of the Eiffel Tower would only hit you with the same force as if dropped from 20 ft or so - still ouch, but certainly wouldn't kill you. This was demonstrated in the American TV show Mythbusters where they dis-proved the same myth about dropping a coin off the top of the Empire State building!

[kempie]

KRUSTY - Consider the contradiction in your first sentence; 'become "weightless"... [and] ...still weigh the same'.

Weight is the result of a gravitational force acting upon a mass. As the strength of the force changes so too does weight.

Also '...the lack of gravity in space' - how do you explain this reduction of the gravitational force? [Hint: it has something to do with distance].

[shammydodger]

There is no lack of gravity in space. It is just of a lesser magnitude. Astronauts/cosmonauts are still attracted by the earth's gravity. Otherwise they would not orbit, but simply float off into space. The condition of "weightlessness" is not due to so-called "zero gravity" although, as a mediocre physicist, I would not wish to try to explain in full here. Try googling for a scientific explanation.

The acceleration due to gravity, or what we commonly refer to simply as "gravity", increases slightly but perceptibly as one gets closer to the earth's centre. Thus, the gravitational pull on a man stood at the peak of Everest is slightly less than it is when he is stood at sea level. Similarly, it is slightly less at the top of the Eiffel Tower than at the bottom. Thus, a pound coin will have more weight at the bottom of the Tower than at the top, but this won't be due to it's speed built up as it falls. The difference will also be so small that very sensitive instrumentation would be required to show it up.

[shammydodger]

Just googled it myself and, if Wikipedia is to be believed (which is not always the case, as some of us appreciate), then the acceleration due to gravity is only 3% less at an altitude of 100km than at sea level.

[jake-the-peg]

Astronauts do not become weightles due to a lack of gravity in space

If there were no gravity in space what do you suppose keeps the moon in orbit?

Astronauts experience weightlessness because they are in free-fall. Like a cannonball fired from a tall tower they fall. Only they are moving fast enough to fall "around" the Earth. like this:

http://www.noao.edu/outreach/nop/tools/cannon.jpg

[shammydodger]

Jake

Thanks for the support :)

[kempie]

"Weightlessness" is not only experienced by bodies in orbit (due to the continuous free-fall as described).

The crews of the Apollo missions also experienced "weightlessness" during the Trans-Lunar Injection phase of their flight when they reached the point where the Moon's gravity negated that of the Earth. At this altitude (approximately 300,000km) acceleration due to Earth's gravity is 99.95% less (or 0.05%) of that at sea-level.

[bernardo]

LotusEater you are obviously very ignorant of basic physics. The reason why I said that it would increase in weight as it gets closer to the centre of the Earth is because it would increase in weight as it gets closer to the centre of the Earth.

g = GMm/d^2

[Space]

you wouldn't trow a pound coin there anyway. You would throw 1.5 euro.

[Geo1000]

In a Rag Week at Uni I was barefoot in the procession through town and got hit on the foot by a 50p coin dropped from 12 floors up. It didnt do 'serious' damage but i could hardly walk for a week!

[LotusEater]

Apologies.