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What's your basic understanding of gravity?


paddy
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If you drop two objects of the same size and shape but different weights from the same height which will hit the ground first?  

87 members have voted

  1. 1. If you drop two objects of the same size and shape but different weights from the same height which will hit the ground first?

    • The heavier item
      37
    • The lighter item
      1
    • They will hit the floor at the same time
      49


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I assumed everyone knew the very basics of gravity until I found out my Mum (who's in here 50s and an intelligent person) didn't the other day, and then today when speaking to someone else (another member of this forum actually) they didn't either. So I'm just wondering if they're in the minority or not? I assumed everyone understood the basics, obviously not.

So if you drop two objects of the same size and shape but different weights from the same height which will hit the floor first?

Please vote before looking at the results otherwise it makes it a bit pointless. It's all anonymous so you won't be making a fool of yourself!

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The answer for the sake of of not spoiling it for anyone, I think anyway

IIRC, gravity reacts equally on all objects, no matter their mass, thus they'd hit the floor at the same time. (The thing that slows objects of differing weights is air resistance... the ultimate proof of this being the hammer and feather drop on the moon that evidenced that air was the factor that slows things - in a vacuum the only factor can be gravity, and a hammer and feather will hit the deck at the same time in a vacuum).
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This reminds me of this simple bit of physics...

If you fired a gun parallel to perfectly flat ground, and at the exact moment the trigger was pulled you dropped an identical bullet from same height, which would the ground first?

The answer seems obvious - they hit the ground at the same time. But an awful lot of people think the dropped one hits first, as if momentum can completely outfox gravity alone.

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Following a "best out of 5" experiment with my wallet and a pencil, I have concluded:

1) they will both hit my foot at the same time.

2) that **** hurt, I need to not drop stuff like a spacker.

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Surely if you dont know the answer to this you are a **** idiot? Its middle school level physics at most. If you drop a cricket ball and a safe full of bricks off the top of a skyscraper, they will both hit the ground at the same time. You will probably go to prison of course, but they will both hit the ground at the same time.

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Everyone knows the basics, everyone is usually also wrong in applying them to situations where gravity isn't the only factor.

In a vacuum it is true that they'll both hit the ground at the same time.

Outside of a vacuum (and this question doesn't specify a vacuum so we'll assume it's outside of one) the heavier object will hit the ground first as it will take longer for air resistance to build up to match the force due to gravitational acceleration and so the heavier object will have a higher terminal velocity, will therefore reach a higher speed, and will hit the ground first.

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Everyone knows the basics, everyone is usually also wrong in applying them to situations where gravity isn't the only factor.

In a vacuum it is true that they'll both hit the ground at the same time.

Outside of a vacuum (and this question doesn't specify a vacuum so we'll assume it's outside of one) the heavier object will hit the ground first as it will take longer for air resistance to build up to match the force due to gravitational acceleration and so the heavier object will have a higher terminal velocity, will therefore reach a higher speed, and will hit the ground first.

I don't feel so stupid now.

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Surely if you dont know the answer to this you are a **** idiot?

I agree. And an awful lot of people ignore air resistance and wrongly think that density isn't a component in aerodynamic drag ;)

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Surely if you dont know the answer to this you are a **** idiot? Its middle school level physics at most. If you drop a cricket ball and a safe full of bricks off the top of a skyscraper, they will both hit the ground at the same time. You will probably go to prison of course, but they will both hit the ground at the same time.

But what if you dropped said items from the top of said skyscraper and you were too high up to see them hit the floor and there was no around for miles at ground-level to see them hit the floor, would they ever actually hit the floor?

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Which is why I chose a cricket ball as my "light" example.

If the safe full of bricks and the cricket ball hit the ground at the same time it will because by some miracle the drag on both of them is equal as the ball is more aerodynamic but lighter. In 99.999999999999999999% of cases that won't be the case, and one will hit the ground first, as to which it'd be, you'd have to work out their terminal velocities to find out.

I always thought it was the lighter because it had less force acting against it. Unless i'm confusing it with another branch of physics completely.

Nope.

What you want is one of the most well known equations, f = ma, the force acting downwards on the heavier object is going to be higher than the lighter object due to the higher mass.

The drag on both objects is going to be the same at the start.

Each object will stop accelerating when the drag is equal to ma, which happens far faster for the lighter object.

The heavier object will also accelerate quicker, as as soon as they start moving the drag counteracts a larger portion of the force due to gravity on the lighter object.

Of course if you're dropping things from a low distance then there isn't the time for drag to play a big enough part to make a visible difference, so dropping things off your desk isn't really a good experiment to see it in effect ;)

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This reminds me of this simple bit of physics...

If you fired a gun parallel to perfectly flat ground, and at the exact moment the trigger was pulled you dropped an identical bullet from same height, which would the ground first?

The answer seems obvious - they hit the ground at the same time. But an awful lot of people think the dropped one hits first, as if momentum can completely outfox gravity alone.

I don't understand this. Surely you mean perpendicular?

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