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What happens when I throw a ball in the air?

  1. Dec 14, 2004 #1
    I have a general physics question that has been bugging me for a while. I should point out that I'm not a pysicist, so any answers need to be in very simple noddy terms that any idiot can understand. :smile:

    My questions is this:
    If I throw something into the air it comes back down in my hand. If I were able to throw it a really long way into the air, exactly perpendicular to the ground, would it still come back down in my hand, or, would the Earth have spun a little causing it to drop somewhere else?

    I asked this to a friend who has some physics training and he suggested it would come back down in my hand still becuase of the atmosphere. Is this correct?

    My real reason for asking is that everytime I get on a Jumbo Jet to travel accross the Atlantic I wonder if the spin of the Earth makes the trip home to London quicker, and if so by how much?

    Thanks to anyone who can explain this to me.
     
  2. jcsd
  3. Dec 14, 2004 #2

    HallsofIvy

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    What your friend meant by "because of the atmosphere" is that the atmosphere moves with the earth. You could not, as I have heard said, go up in a balloon and then wait while the earth revolved under you! The balloon moves with the air which moves with the earth.

    Without the atmosphere, the answer might be a little different. When you are standing on the surface of the earth, you are revolving with it: your eastward speed is exactly the same as the surface of the earth (and so is the speed of the ball in your hand. As the ball moves upward, it retains that motion BUT, since the radius of the circle it is describing eastward is now longer, moving the same speed to the east results in a smaller angle: The ball would, in fact, fall slightly westward of you!
    (That is a variation on "coriolis" force.)
     
  4. Dec 15, 2004 #3
    >You could not, as I have heard said, go up in a balloon and then wait while the earth revolved under you! The balloon moves with the air which moves with the earth.

    You can under the right conditions. National Geographic magazine featured a story and pictures of a manned high altitude balloon that circumnavigated the earth. The jet stream will carry one along at a high speed for non powered flight, (relative to the earth's surface). The biggest obstacle was getting permission from some of the middle east countries to "fly" over them.
     
  5. Dec 16, 2004 #4

    DaveC426913

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    "...everytime I get on a Jumbo Jet to travel accross the Atlantic I wonder if the spin of the Earth makes the trip home to London quicker, and if so by how much?..."

    It would be true of the Jumbo were floating in space, and the Earth turned under it. As to how much quicker the trip would be, it would simply a matter of how much the Earth rotated while you are in the air, which is 15 degrees for every hour of flight. Depending on how far you live from the equator, that will be between 0 and 1000 miles for each hour in flight.

    New York to Paris is approx. straight across the 45th parallel, and about 3500 miles. So, during a 7 hour flight (3500mi X 500mph), the Earth turns 35 degrees. For you, that's (35*sin(45))= 2350 miles. Your trip to New York is only (3500-2350)=1150 miles! Of course, your trip back would be (3500+2350)=5850 miles.


    *However*, that is not the case, as the jet *does* move *with* the Earth. It *started* on the Earth, and it's moving in the atmosphere on the Earth, and it's going to stop on the Earth. There's no reason for it to suddenly stop being affected by the Earth once it is in flight.

    The real reason your flight times change is due to headwinds and tailwinds. A 50 mph wind will either add or subtract that speed directly from your air speed. So, 450mph one way (8h45m), and 550mph (6h35m) the other way - that's a 2+ hour difference!
     
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