Say a meteorite was falling in the earth's atmosphere and it finally reaches the ground and it is about a quarter of an inch when it hit the ground. How big do you think that meteorite was when it was in space? If that little rock hit someone on the top of the head do you think they would die?
This is the same principal as the penny falling from the Empire State Building. If I were to throw a penny at your head (which would be pretty hard since you're in California and I'm in New York), it probably would not kill you, just hurt like the dickens. If I dropped a penny from the top of the Empire State Building and you were standing on the street below, it would go right through your skull killing you instantly.
If someone threw a meteorite at you, it would hurt, but one falling from the sky getting sucked down by the force of gravity, you'd be killed, just like with the penny. ************************************************************ 11-06-02, 06:17 PM gerry I don't know just how big that meteor was when it first started.....most of it got burnt entering earth's atmosphere. I suspect that for any of it to make it through the fireball, i's initial size was substantial. But falling on your head thru the air at a quarter inch diameter, it would have reached a terminal velocity that depends on how much it weighed. Assuming it weighed that of a pebble, it would hit your head at about oh say 40 mph (by the way, the terminal velocity of the penny falling from the Empire State Bldg. is about 25 mph), and man oh man it would smart a bit, but very unlikely would it kill you. Nor would that falling penny kill, you would more likely be hurt by it when thrown at you.
11-06-02, 09:16 PM Minnesota Terminal velocity has nothing to do with the speed of a meteorite. Meteoroids travel anywhere from 27,000 to 160,000 mph in outer space. Consequently, when they enter our atmosphere they are traveling far in excess of an object simply dropped from that height. Barringer crater in Arizona, for example, was hit by a meteorite estimated to be traveling at 40,000 mph. Of course it is impossible to determine the speed of a meteorite only a quarter of an inch in diameter--one has to know the size of the parent meteoroid, its angle of entry, and the relative motion of the earth to its trajectory. Almost surely it would crash through a person's skull, killing them.
11-07-02, 04:55 AM JoMS At meteoric speeds, it would be in the atmosphere for less than two seconds. Not much time to burn anything up. Air friction would slow it, but not by a lot in this short a time.
11-07-02, 11:47 AM Julieta Martinez The reason I ask this question because when I was little, I was in the playground and I got hit on the top of my head by a rock and I looked around to see who threw it at me and no one was there! So I have had this in the back of my mind for awhile, and I thought I would just ask.
Oh, and by the way, it did hurt a lot!!!!!
11-07-02, 01:11 PM frankvan Meteorites travel in orbits around the sun at velocities of 10 to 30 miles per second. To collide with the earth it must first penetrate our atmosphere. During the high speed penetration the air does not have time to move aside so the meteorite acts like a piston compressing the air in front of it. The heat resulting from this compression causes the meteorite to melt and burn. Small meteorites never survive the journey, they filter down as small particles of dust and ash. If it burns up it is a "shooting star" or meteor. If it hits you it was big enough to survive the trip and is still a meteorite and it still kills you. The consensus, I believe, that was no meteorite that hit you on the head, Julieta. wink
11-07-02, 03:09 PM gerry "Shooting Stars" are meteors that burn up as they enter the atmosphere at meteoric speeds. Do not underestimate the power of earth's air! Assuming a 1/4 inch 'pebble' (we're not talking the Rock of Gibraltar here, just a tiny stone) got thru the fireball, moving at say 50,000 mph at 100 miles up, air would exert a force on it depending on the air pressure, that would vary from near 0 at 100 miles up to 15 psi at earths surface. Assuming an average air pressure during its trajectory to earth of 7 psi, this equates to a force on the 1/4 inch stone of about 1200 pounds, which would reduce to the pebble's weight at near surface, for an average force acting on the pebble due to air of 600 pounds. Using the pebble meteor's weight at about 1/2 an ounce, this air force would decelerate the pebble dramatically, until it reached its terminal velocity and rather harmlessly rapped your skull.
11-07-02, 09:06 PM Minnesota Just a reminder about the terminology
Meteoroid: Any natural space object that is due to collide with a planet. It is also sometimes used to denote asteroids with a diameter less than a kilometer (2/3 of a mile).
Meteor: the blazing phenomenon created when a meteoroid enters an atmosphere and ram pressure (not friction) quickly heats the atmospheric gases in front of it to an incandescent temperature, which in turn causes the surface of the body to melt.
Shooting star: a meteor with an observed brightness equal to or greater than that of Venus.
Meteorite: any natural object from space that makes contact with a planet's surface.
Meteoroids, meteors, shooting stars, and meteorites that occur in conjunction with Earth may come from comets, asteroids, and Lunar and Martian ejecta.
11-08-02, 10:51 AM Julieta Martinez Thanks guys... just wondering....
11-08-02, 04:16 PM MkStfnz
quote:Originally posted by gerry: Nor would that falling penny kill, you would more likely be hurt by it when thrown at you.
It might not kill you, but more than likely it would become lodged into one's skull. If this wouldn't kill you, it would certainly do serious damage to the brain.
11-08-02, 04:47 PM gerry Many a baseball player have been hit by a Clemens' 90 mph fastball and survived with just a bruise. I think a 25 mph penny will do not neary as much damage. Heck, Conigliaro took a 95 mph fastball to the eye, and made a great try at a comeback, only to die years later from presumably unrelated causes.
My revised calcs show the terminal velocity of the 1/4 inch meteor/meteorite/meteor whatever you call it to be in the 150 mph range, still very unikely to penetrate thru your skull.
11-08-02, 06:25 PM gatman Think it would matter if that penny hit you heads up or tails? Might make a definate impression but how about if it hit you on the thin side?
11-12-02, 06:45 PM gerry Yes, if the penny were to fall on its thin side throughout its decent, its terminal velocity would be close to 70 mph, since less surface would be exposed to the air. Falling flat, about 25 mph is the terminal velocity. In actuality, the penny is likely to rotate as it falls, placing its terminal velocity some where in between these two values.
11-12-02, 08:59 PM cattywampus I saw the Meteor Crater several times when I lived in Arizona. It is owned by a private family that charges admission to see it, and they've been living off it for years and years. It is an awesome site/sight. I also saw the meteor. It kind of boggled me because it was/is composed largely of nickel and we seldom see nickel in its natural state - not that big, anyway. It was about the size of a smallish kitchen table.
Catty (hmmmm. Is this on topic? No! Yikes! Don't hit me! Helllllllp!) big grin
11-13-02, 10:07 AM methos it wasn't an extremely controlled experiment, but i read an account of someone experiemntally determining the terminal velocity of a penny to be 45 mph, so gerry's 25-70 mph result sounds right.
This message has been edited. Last edited by: DorianGreyed,
Posts: 5457 | Location: USA | Registered: 06-24-02
Apr 1, 1930 Leo Hartnett (Gabby Hartnett) of the Chicago Cubs broke the altitude record for a catch by catching a baseball dropped from the Goodyear blimp 800 feet over Los Angeles, CA. He caught the ball cleanly, saying, "Eeeeooooww!". His injuries included a broken jaw. -------- Joe Sprinz was behind the plate for 158 of the team’s 191 games. He played most of the next seven years in the American Association with very brief major league stays with the Indians and Cardinals. Sprinz returned to the PCL in 1936 with the Missions and rejoined the Seals in 1938. He became famous for an incident that took place on his 37th birthday, August 3, 1939. Dobbins writes, “With the Seals in the thick of the pennant race and the World’s Fair being held on Treasure Island in the middle of San Francisco Bay, the great hustler Walter Mails negotiated a stunt in which the Seals catcher would catch baseballs thrown by (manager) Lefty O’Doul from the 450-foot high Tower of the Sun. Sprinz caught five balls, (Larry) Woodall caught three. The event was a success, but Mails, not satisfied, negotiated the “Great Balloon Drop,” in which the catchers would attempt to catch balls thrown from a blimp circling 1,000 feet above the baseball diamond on Treasure Island. A large crowd was on hand. Neither Woodall nor Sprinz was enthused about the stunt. When the signal came to start the drop everybody backed away, leaving Sprinz standing alone. The first ball landed in empty bleachers. The second embedded itself in the field. That should have been a clue for Sprinz, but he went on. With glove held above his head, he tried to keep up with the (third) ball but misjudged it. The ball glanced off his mitt, crashing into the side of his face. Sprinz awoke in the hospital with 12 broken bones, a badly lacerated face and five teeth knocked out. It was later estimated the ball was traveling 150 miles an hour.” Sprinz ended up with a line in the Guinness Book of Records (highest catch attempted), three months in the hospital and five years of headaches. -------- Problem: In 1938, Joe Sprinz of the San Francisco Baseball Club attempted to break the record for catching a baseball dropped from the greatest height. Members of the Cleveland Indians had set the record the preceeding year when they caught baseballs dropped about 230 meters from atop a building. Sprinz used a blimp at 260 meters. Ignore the effects of air on the ball. Find the time of its fall, and the speed of its impact.
This problem is part only of a problem found in Fundamentals of Physics, Chapter 2, Page 30, 4th Edition (John Wiley & Sons, 1993) by Halliday, Resnick, and Walker.
The Newtonian time elapsed is dt = 7.28 seconds, and the final velocity is vf = -71.38 meters per second. That is -159 miles per hour. - Dept. of Physics & Astronomy, University of Missouri- St. Louis -------- Weight of official baseball (from MLB rules) - " not less than five nor more than 5 1/4 ounces avoirdupois" *********************************************************** 10-18-06, 06:55 PM frankvan Isn't it obvious that a meteorite enters the earth's atmosphere at velocities of thousands of miles per hour, and at something other than perpendicular to the earth ? A body in motion persists in motion ---etc. Talk of terminal velocity of a meteorite is no more sensible than comparison to an object dropped from great height. In addition to the force of gravity upon a meteorite there must obviously be an angular vector present up 'til the time the acceleration of gravity causes impact with the ground. or the victim's skull. I say that was no meteorite that hit the lady's head. Perhaps it was a piece of ice dropped from a passing airplane?? Where is minnesota when I need him?
Oops, scratch that airplane, make it a helicopter, hovering. Otherwise the same objection about the meteorite. Object not traveling in vertical direction alone; has resultant of two velocities. Wink
10-18-06, 08:27 PM methos The "etc." is important there... "unless acted upon by an unbalanced force." Friction is such a force. Is it so hard to believe that a force strong enough to incinerate most of a chunk of rock a couple hundred yards in diameter is also capable of slowing the remaining chunks down?
Large meteorites will have too much momentum to be slowed significantly. A quarter inch one will not. (That's not to say that I actually think that what hit Julieta was a meteorite.)
10-19-06, 09:32 AM frankvan Perhaps we would have to ask Julieta to allow us to examine her skull, if she is still alive and available. But, in spite of the prestigious opinions expressed, I still contend that "terminal velocity" is still some finite velocity, not a standstill condition from which a projectile free falls to earth. Regardless the resistance of air friction, if the object is traveling at 60 mph horizontally and 60 mph vertically, it is traveling at ~ 85mph at a 45 degree angle on impact. Or, am I mistaken as well as obsolete, methos ? Confused
Wait a minute! I think I see what I'm doing. I'm arguing against something that has not been said. The thing can reach some terminal velocity due to air friction without ever having fallen vertically, period! It can just hit Julieta's head at some angle at some terminal velocity, unlike one dropped from a stationary building.
This message has been edited. Last edited by: frankvan, 10-19-06 11:50 AM
10-19-06, 11:24 AM DorianGreyed meteorite "Perhaps it was a piece of ice dropped from a passing airplane?? Where is minnesota when I need him?"
I suggest a more likely solution. I think one of Julieta's friends just ducked.
10-19-06, 06:31 PM Julieta Martinez Yep, I¨m here and willing for you to examine my skull. I think someone hit me and ducked.... you´re right DG. Kids can be mean. Smile
10-19-06, 07:13 PM frankvan Thank heaven you're still alive. I sincerely hope you'll visit more often than every four years. Wink Could that bump have been more severe than we first thought?
10-21-06, 08:13 PM Julieta Martinez HAHA! Thanks. The reason I stopped coming is I moved from Los Angeles where I had an internet connection at home, to a small rural town in Mexico where there is no running water let alone an internet connection. I come online only when I am in the city. Sad isn´t it.
This message has been edited. Last edited by: DorianGreyed,
Posts: 17570 | Location: Lincoln Place, Granite City, IL, USA | Registered: 06-03-02
Isn't it obvious that a meteorite enters the earth's atmosphere at velocities of thousands of miles per hour, and at something other than perpendicular to the earth ? A body in motion persists in motion ---etc. Talk of terminal velocity of a meteorite is no more sensible than comparison to an object dropped from great height. In addition to the force of gravity upon a meteorite there must obviously be an angular vector present up 'til the time the acceleration of gravity causes impact with the ground. or the victim's skull. I say that was no meteorite that hit the lady's head. Perhaps it was a piece of ice dropped from a passing airplane?? Where is minnesota when I need him?
Oops, scratch that airplane, make it a helicopter, hovering. Otherwise the same objection about the meteorite. Object not traveling in vertical direction alone; has resultant of two velocities.
The "etc." is important there... "unless acted upon by an unbalanced force." Friction is such a force. Is it so hard to believe that a force strong enough to incinerate most of a chunk of rock a couple hundred yards in diameter is also capable of slowing the remaining chunks down?
Large meteorites will have too much momentum to be slowed significantly. A quarter inch one will not. (That's not to say that I actually think that what hit Julieta was a meteorite.)
Perhaps we would have to ask Julieta to allow us to examine her skull, if she is still alive and available. But, in spite of the prestigious opinions expressed, I still contend that "terminal velocity" is still some finite velocity, not a standstill condition from which a projectile free falls to earth. Regardless the resistance of air friction, if the object is traveling at 60 mph horizontally and 60 mph vertically, it is traveling at ~ 85mph at a 45 degree angle on impact. Or, am I mistaken as well as obsolete, methos ?
Wait a minute! I think I see what I'm doing. I'm arguing against something that has not been said. The thing can reach some terminal velocity due to air friction without ever having fallen vertically, period! It can just hit Julieta's head at some angle at some terminal velocity, unlike one dropped from a stationary building.
This message has been edited. Last edited by: frankvan,
Thank heaven you're still alive. I sincerely hope you'll visit more often than every four years. Could that bump have been more severe than we first thought?
HAHA! Thanks. The reason I stopped coming is I moved from Los Angeles where I had an internet connection at home, to a small rural town in Mexico where there is no running water let alone an internet connection. I come online only when I am in the city. Sad isn´t it.
