# ♻ PLASTIC BOTTLE RAIN GAUGE ♻

This is a simple rain gauge made from a plastic bottle. My father tought me how to do it.
We always use it for deciding if and when we should water our fruit trees. (keep in mind that on a hot summer day 4 or 5 mm of water a day evaporated from the ground, so if it rained 50 mm, you don't need to water your trees for about 10/12 days).
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## Step 1: WHAT YOU NEED

MATERIALS:
_plastic bottle (conic or funnel shaped);
_strong tape;
_stick or cane.
TOOLS:
_cutter;
_permanent marker;
_scales or capacity measure for liquids;
_ruler.

## Step 2: PREPARE BOTTLE

remove labels  with warm water, and cut away the bottom of the bottle with cutter.

## Step 3: MAKE MESUREMENT

_measure the open AREA of the bottle opening:  r • r • 3.14 (measure the diameter, divided it in 2 and find the radius, then
_now, knowing that if it rain 1l of water on 1 square meter it will correspond at 1 mm of water, we need to find out how many ml in your bottle that mm of rain fall on the ground will correspond  (x).  We need to use this formula:

1m2           bottle open area                                    1liter   •  bottle open area
--------   =    ---------------------               so:            x= ----------------------------------
1 liter                    x                                                                 1m2

this is an example using the measurement of my bottle, my bottle diameter was 8.6 cm ( than 4.3 cm of radius)
4.3cm•4.3cm•3.14=58cm2                ( 58cm2=0.0058m2)

1m2           0.0058m2                                            1 liter • 0.0058 m2
---------  = ------------------                   so:           x= ---------------------------         so:       x=5.8 ml
1 liter               x                                                             1m2

another way to find your x  is: calculate the volume of 1 mm of water on the area of open surface of your water bottle, and use that number to make the measurements on your bottle:
r•r•3.14•0.1cm2=x    (than transform it: 1cm2=1ml)
Kiteman1 year ago
Er... Why do you start your sentences with an underscore instead of a capital letter?
marcellahella (author)  Kiteman1 year ago
Because each sentences with an underscore is a step (and so I wanted to mark them)... but I also forgot to use the capital letter.
mathiemom1 year ago
Love the math!!
marcellahella (author)  mathiemom1 year ago
Thanks
wazzup1052 years ago
Why have I never made one of these... probably the math part .... Now there's no reason left :)
dchall82 years ago
Excellent use of math to solve a tricky problem.
Lorddrake2 years ago
Very nicely done.

FYI you have a typo in step 3 ..
it should say 4.3cm•4.3cm•3.14=58cm2 not 4.6cm•4.6cm•3.14=58cm2
marcellahella (author)  Lorddrake2 years ago
thanks, i m going to change it immediately, thank for saying it!
marcellahella (author)  marcellahella2 years ago
please if anyone see other mistake or incomprehensible things please let me know