Half A Second

[jon1968]

I’m trying to explain how close a 100m race is even though on the telly it looks likes there’s a distance between sprinters! There’s sometimes half a second between first and last. It's longer than a blink but....

So, how high off the ground would I have to hold a tin of baked beans (or any other readily available produce) in order to demonstrate how long half a second is between release and impact? Many thanks.

[factor-fiction]

1.24 metres?

[Spoonboy]

Not that far I should think: maybe half a foot. Or less.

[bibblebub]

ignoring air resistance, d = 1/2 g t²

so 1/2 second gives about 4 feet

[factor-fiction]

I did it in my head initially.

Use distance = 0.5gt² where g= 9.8 m/s²
Answer 1.22m -
Yes, close to 4 feet

This ignores air resistance and assumes starting velocity was 0

[Svejk]

Its 100 beats of a fly's wing, if that's any easier.

[factor-fiction]

Is that more or less than two shakes of a lamb's tail?

[jim360]

Half a second is approximately the time it takes for light to travel around the world three-and-half times...

[Spoonboy]

At last Jim, there is something that's faster than Bolt!

[Mattk]

To keep it simple it takes 10 seconds to run 100m therefore it takes 1 second to run 10 metres and 0.1 seconds to run 1 metre. Half a second is therefore approx 5 metres.

These are of course very rough averages but helps to explain.

[factor-fiction]

^ but the question is about dropping a baked beans tin

[factor-fiction]

Sorry, I see what you mean- another way of explaining half a second. Yes, that's probably a better way. Although as we can't run that fast it may be better to say we'd run 1-2 metres in that time

[dr b]

"but the question is about dropping a baked beans tin". I wonder if that's the first time in human history that that sentence has ever been typed or spoken.

[Spoonboy]

Could be dr b. It's a nice change than dropping one's aitches, don't you think?!

[jomifl]

Is it a full or empty BB tin and what size?

[jomifl]

@ 32feet per sec squared, It still has to travel 28 feet in the next half second, somehting wrong surely?

[nescio]

jomifl,
32 feet per second squared is the rate of acceleration - i.e. the speed increases by 32 feet per second, each second. Therefore, there is nothing wrong.
Incidentally, it makes no difference whether the tin is full or empty - the acceleration is independent of mass.

[jomifl]

Nescio, Thanks for making me think about it, it has all become a lot clearer :-)

[Svejk]

I've never believed that feather & cannonball business.Doesn't make sense.

[mibn2cweus]

In the time of Aristotle, it was presumed that the speed at which an object fell was entirely down to the weight of the object and that speed was instantaneous and constant throughout the fall. So sure were they of these (obvious) conclusions that they never felt compelled to do an experiment . . .

WARNING: You might want to turn the volume down (or off) before running this Youtube video - http://tinyurl.com/kyfabfx

[jim360]

The only thing mass affects is the maximum speed that can be reached by any object. Eventually, in air a feather will fall at a far slower speed than a cannonball. But the acceleration due to gravity is the same (acceleration can be affected by air as well, though). Take away the air and the two will fall at the same speed, as was demonstrated on the Moon.