07 Jun 07
1 edit
Originally posted by Restless SoulThen why is the lawn green?
because if it was green people wouldn't know where to stop mowing their lawn.
Answer: When the yellow light from the sun is blended with the blue light from the sky then you get green, and that's why the laws is green.
07 Jun 07
Originally posted by RamnedYou could simply look at the texture of the ground.
Yes, good.
Power = work / time. Time = 1, so here power = work.
Work = Distance * Force. Distance = 9 so Work = 9*Force
Force = Mass(Acceleration). Acceleration = 10 (gravity.) Mass = 60 (600 is weight -> /10 and 60 is mass). Force = 600.
So Work = 9*600, Work = 5400. Power = 5400. Done. (Isn't that a bit more simple, just use the Force = Mass * Acce ...[text shortened]... e still have #1-#2. (tension is the other variable in #10). Then I'll post the hardest I know.
now...
07 Jun 07
Originally posted by Restless SoulBlue flowers are not pollinated by insects.
if the lawn was blue airplanes wouldn't know where to land
Because if insects would be attracted to the blue colour, then they would fly to the sky.
Can anyone entomologist/botanist confirm this?
07 Jun 07
Originally posted by FabianFnasSome bee flowers tend to be yellow or blue, often with ultraviolet nectar guides and scent.
Blue flowers are not pollinated by insects.
Because if insects would be attracted to the blue colour, then they would fly to the sky.
Can anyone entomologist/botanist confirm this?
http://en.wikipedia.org/wiki/Pollination_syndrome
08 Jun 07
Originally posted by mtthwtension covers that. The edges are more tense than the middle = tension.
You missed one - where you pluck it. That determines which harmonics the string vibrates at. E.g. compare plucking it in the middle with plucking it a quarter of the way along.
So, #1-#2 - who knows those tricky mirror questions?
08 Jun 07
3 edits
Originally posted by RamnedKnows them, or knows the idea behind them?
tension covers that. The edges are more tense than the middle = tension.
So, #1-#2 - who knows those tricky mirror questions?
edit1: 1. C.
It just depends upon the distance of the mirror from you or the object.
edit2: sorry. need a deeper explanation.
If the distance between you and the mirror is greater than the distance of the focal point from the mirrors parabola, then you are seeing a virtual.
If the distance between you and the mirror is less than the distance of the focal point to its corresponding curve, the image is real
08 Jun 07
1 edit
Originally posted by RamnedNo it doesn't. The tension is the same everywhere (neglecting some minor effects like gravity). Think about balancing the forces on a section of the string - the forces at each end (in other words the tension at each end) must cancel out. This applies to any section of string, so the tension is constant.
tension covers that. The edges are more tense than the middle = tension.
Pluck a string in the middle and you get the first harmonic. Pluck it a quarter of the way along and you'll get the second harmonic - half the wavelength and twice the frequency. Pluck it somewhere in between and you'll get a mixture of harmonics.
08 Jun 07
Originally posted by mtthwIt's true! I've popped many a squealie in my lifetime.
No it doesn't. The tension is the same everywhere (neglecting some minor effects like gravity). Think about balancing the forces on a section of the string - the forces at each end (in other words the tension at each end) must cancel out. This applies to any section of string, so the tension is constant.
Pluck a string in the middle and you get the first ...[text shortened]... nd twice the frequency. Pluck it somewhere in between and you'll get a mixture of harmonics.
08 Jun 07
Originally posted by mtthwUnless you can pluck the string in such a way that just before you let go it is shaped exactly like a sine wave then you won't get a pure harmonic no matter where you pluck it; although how important each harmonic is is going to depend on where it's plucked.
Pluck a string in the middle and you get the first harmonic. Pluck it a quarter of the way along and you'll get the second harmonic - half the wavelength and twice the frequency. Pluck it somewhere in between and you'll get a mixture of harmonics.
I double checked the statement about tension on Wikipedia before posting and couldn't find any statement to contradict what we are saying about it being uniform along the string, but while I was looking I found this:
http://en.wikipedia.org/wiki/Vibrating_string
Which gives a nice puzzle for the thread. Why is the derivation of the speed of waves on the string wrong? And why does the author happen to get the right answer?
08 Jun 07
Originally posted by DeepThoughtTrue, I was simplifying.
Unless you can pluck the string in such a way that just before you let go it is shaped exactly like a sine wave then you won't get a pure harmonic no matter where you pluck it; although how important each harmonic is is going to depend on where it's plucked.
I double checked the statement about tension on Wikipedia before posting and couldn't find any ...[text shortened]... speed of waves on the string wrong? And why does the author happen to get the right answer?
As for the last bit - well spotted! Centripetal force for something that isn't rotating? I don't think so. Dimensional analysis tells you the answer is going to be right to within a constant multiplier though. Which happens to be 1, though that may be coincidence.