This is a good - book.Take a book from the table.Put this - book into the bookcase. The weather is fine today. The sky is blue. The sun is shining brightly in the blue ...sky.This is a boy. The boy is at - school.He is a pupil.This - boy is my- brother's - friend.He has a cat,but he has no - dog.He likes his(?) - cat.He gives the cat - milk every day.Yesterday I reseived a letter from my - friend. The letter was interesting.We live in a big house.I like the house very much.Are you a worker?-no,I am a student.I like your a beautiful - flower.Give me the flower,please.My - mother is at - home.She is reading an interesting - book.My father is not at - home.He is at - work.He is a doctor.He is a good - doctor.He works at a hospital. The hospital is large.
1) Density is measured in kilograms per cubic meter.
2) Most materials have a higher density than water and sink in water.
3) The density of the material is very important, especially in aviation.
4) Young's modulus is the ratio of the applied force to the elastic deformation of a given material.
5) The more rigid the metal, the less it deforms under load.
6) when the metal is stretched, it first flows, that is, it is plastically deformed.
7) Lead, copper, aluminum and gold are the most malleable metals.
8) Creep resistance is a very important property of materials used in aircraft engines.
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