the outside of the shape
Displacement
If you wanted to describe the length and breadth of an irregular shape you would find the maximum length and breadth. You could sandwich the object between two flat boards, and measure the distance between the boards. Then rotate the object 90o and do it again, for the breadth.
It depends on the shape of the area. If the shape is a square, each side would measure about 120 feet.
You would use square inches if you were trying to measure the area of a 2D shape.
Usually it gets bigger, if you wanted to do an experement, you would- Measure the spring, put it in water, take it out then measure it again and it would be bigger!
Weigh it & measure its volume.
It depends on what shape the 2.1 acres is. However, if the shape is a square, then each side would measure 302.45 feet.
If you wanted to use English Units you would want to use feet or inches. If you wanted to use the metric system you would want to use centimeters.
Grams is a measure of weight so you would not use that. If you measure the depth, width and length of the pool in metres, you will be able to calculate the volume in litres.Every stere (cubic metre) is 1,000 litres.
energy release
Idepends on what characteristic of the bananas you wanted to measure: their mass, volume, spread (useful for packing).
Most mathematicians would refer to it as a 666-gon. If someone wanted to be pretentious, or unhelpful, they could call it a hexahectahexacontakaihexagon.