Advertisements
Advertisements
प्रश्न
A SONAR (sound navigation and ranging) uses ultrasonic waves to detect and locate objects under water. In a submarine equipped with a SONAR the time delay between generation of a probe wave and the reception of its echo after reflection from an enemy submarine is found to be 77.0 s. What is the distance of the enemy submarine? (Speed of sound in water = 1450 m s–1).
Advertisements
उत्तर १
Let the distance between the ship and the enemy submarine be ‘S’.
Speed of sound in water = 1450 m/s
Time lag between transmission and reception of Sonar waves = 77 s
In this time lag, sound waves travel a distance which is twice the distance between the ship and the submarine (2S).
Time taken for the sound to reach the submarine = `1/2 xx 77 = 38.5 s`
∴ Distance between the ship and the submarine (S) = 1450 × 38.5 = 55825 m = 55.8 km
उत्तर २
Here speed of sound in water v = 1450 m s-1and time of echo t = 77.0 s.
If distance of enemy submarine be d, then t = 2d/v
∴ d=vt/2 =1450 x 77.0/2 =55825 m=55.8 x 103 m or 55.8 km
संबंधित प्रश्न
Round up the following upto three significant figures:
34.216
Round up the following upto three significant figures:
10.4107
How many significant figures should be present in the answer of the following calculation:-
`(0.02856 xx 298.15 xx 0.112)/0.5785`
How many significant figures should be present in the answer of the following calculation?
0.0125 + 0.7864 + 0.0215
The relative density of lead is 11.3. Its density is ______ g cm–3or ______ kg m–3.
A student measures the thickness of a human hair by looking at it through a microscope of magnification 100. He makes 20 observations and finds that the average width of the hair in the field of view of the microscope is 3.5 mm. What is the estimate on the thickness of hair?
Precise measurements of physical quantities are a need of science. For example, to ascertain the speed of an aircraft, one must have an accurate method to find its positions at closely separated instants of time. This was the actual motivation behind the discovery of radar in World War II. Think of different examples in modern science where precise measurements of length, time, mass etc. are needed. Also, wherever you can, give a quantitative idea of the precision needed.
State the number of significant figures in the following:
2.64 × 1024 kg
State the number of significant figures in the following:
0.0006032 m2
Solve the numerical example.
Write down the number of significant figures in the following: 0.003 m2, 0.1250 gm cm-2, 6.4 x 106 m, 1.6 x 10-19 C, 9.1 x 10-31 kg.
The number of significant figures in 0.06900 is ______.
The numbers 2.745 and 2.735 on rounding off to 3 significant figures will give ______.
Why do we have different units for the same physical quantity?
How many significant figures are present in the measurement 2007 grams?
Which of the following measurements contains exactly two significant figures?
What is the least count of a measuring instrument?
The radius of Earth is expressed as 0.64 × 10⁷ m in scientific notation. What is its order of magnitude and number of significant figures?
Which of the following statements is correct about significant figures and accuracy?
