Physics

Electricity and Magnetism Level 1

If a thunder is heard by a man 4 seconds after the lightning is seen, how far is lightning from the man: (speed of sound in air = 330 m / s e c 330 m/sec )

1320 m 1450 m 1920 m 640 m

Ankit Vijay by Ankit Vijay , 22, India

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3 solutions

Ankit Vijay
Jun 13, 2014

d = v × t = 330 × 4 = 1320 m d = v × t = 330 × 4 = 1320 m

3 Helpful 0 Interesting 0 Brilliant 0 Confused

area is scalar or vector quantity

shivam shukla - 7 years ago

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Area is the product of two lengths. Length is a scalar quantity, the direction in the length is being measured does not influence the measurement. For instance the length of a line drawn between two points A and B is the same for AB as well as BA.

As the product of two scalar quantities is also a scalar quantity, area is a scalar quantity.

Ankit Vijay - 7 years ago

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than why in coordinate geometry sometimes area of triangle is negative

shivam shukla - 6 years, 12 months ago

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@Shivam Shukla – what is a dimensional formula of thermal conductivity

shivam shukla - 6 years, 12 months ago

the moment of inertia of the disc used in a torsional pendulum about the suspension wire is 0.2 kg-m2 it oscillates with a period of 2 sec another disc is placed over the first one and the time period of the system becomes 2.5 sec find the moment of inertia of the second disc about the wire

shivam shukla - 7 years ago

Assuming light takes negligible time to travel, then 4 s 4\space s is the time taken for the sound of thunder to travel to the man. Therefore, the thunder is distance = speed of sound × \times sound traveling time = 300 × 4 = 1320 m =300\times 4 = 1320\space m .

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Shubham Gaikwad
Jun 17, 2014

But light do not travel at infinite speed.

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It would take the light 0.000004403046 seconds to travel 1320m. I think that is negligible.

Sophie Crane - 6 years, 12 months ago

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Indeed, the answer is unchanged (even if you round to many decimal places) if you account for the speed of light. This is assuming that the medium is normal air and that there are no extremely dense objects (such as a black hole) nearby. For that reason it does not matter that light is not infinitely fast.

Caleb Townsend - 6 years, 4 months ago

you are right

shivam shukla - 6 years, 12 months ago

can anybuddy give me a note of theroy of releativity

shivam shukla - 6 years, 11 months ago

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