Question

Write the answer of these questions in one word :
(i) The synthetic fibres are also called
(ii) The wild plants which grow along with the main crop are called
(iii) The force acting per unit area of the surface is called
(iv) Sound having frequencies greater then 20,000 HZ are called ul ​

Answer 1

Answer:

I hope it is helpful for you......✨

Explanation:

1.man-made fibers

2.weeds

4.ultrasound

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Answer 2

(i) a) Synthetic fibres are also called man-made or artificial fibres. b) Synthetic fibres are synthesized from raw-materials called petrochemicals. c) Like synthic fibres, plastic is also a polymer.

(ii) Weeds are the unwanted plants grown with the crop plant (other than the main crop) grown in the soil. They take nutrients from the soil and compete with the main crop. They are removed from the fields by the process of weeding.

(iii) The total force acting perpendicular on a given surface is called thrust. Thrust acting upon a unit area is called pressure.

(iv) Humans with normal hearing can hear sounds between 20 Hz and 20,000 Hz. Frequencies above 20,000 Hz are known as ultrasound. ... At the other end of the spectrum are very low-frequency sounds (below 20 Hz), known as infrasound. Elephants use infrasound for communication, making sounds too low for humans to hear.

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