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CBSE Class 9 Answered

Why do animals like dogs etc get uneasy before earthquakes?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
answered-by-expert Expert Answer

Earthquakes produce low frequency infrasound before the main shock waves begin, therefore the animals like dog which could hear sounds below 20 hz, i.e infrasound get a warning and become disturbed.

Answered by | 04 Jun, 2014, 03:23: PM

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CBSE 9 - Physics
(3 X 3 = 9) CASE STUDY QUESTION 26. Ultrasounds can be used to detect cracks and flaws in metal blocks. Metallic components that are generally used in construction of big structures like buildings, machines and also scientific equipment. The cracks or holes inside metal blocks, which are invisible from outside, reduce the strength of the structure. Ultrasonic waves are allowed to pass through the metal block and detectors are used to detect the transmitted waves. If there is even a small defect, the ultrasound gets reflected back indicating the presence of flaw or defect. Clearly indicated in the figure Defect or flaw Ultrasound Detectors Metal Block (a) The transmitter sends an ultrasound wave of speed 5960m/s through a long steel bridge and a block reflects it back after 0.02s. how far the block in the metal bridge is from the transmitter. (b) With the above property of ultrasound waves, Can ultrasonic waves be used in the medical field? If so, how and give one use in the medical field to justify your answer? (c) Give two practical applications of reflection of sound waves?
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CBSE 9 - Physics
explain human ear with lable diagram
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CBSE 9 - Physics
Can blackbox pings signal travel 3000kms? Can it be reflected on metal surface?
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CBSE 9 - Physics
Sound creates vibrations in our ear. We listen sound and understand it. But after this in which form of energy does it gets converted into? 
Asked by Vishalgarg1234 | 29 Nov, 2018, 07:20: PM
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CBSE 9 - Physics
Why do animals like dogs etc get uneasy before earthquakes?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
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CBSE 9 - Physics
How does a hearing aid work?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
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CBSE 9 - Physics
How is ultrasound used in various industries?
Asked by Topperlearning User | 31 Mar, 2014, 07:23: AM
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CBSE 9 - Physics
Which part of the ear contains the actual hearing organ?
Asked by Topperlearning User | 20 May, 2015, 01:57: PM
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CBSE 9 - Physics
What causes temporary deafness in high altitude flying aircrafts?
Asked by Topperlearning User | 04 Jun, 2014, 01:23: PM
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CBSE 9 - Physics
Draw labelled diagram of auditory parts of human ear and explain how the human ear works.
Asked by Topperlearning User | 20 May, 2015, 02:03: PM
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