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3 years ago

When and why was the metric system invented?

1 answer:

3 0

The first practical realisation of the metric system came in 1799, during the French Revolution, when the existing system of measures, which had become impractical for trade, was replaced by a decimal system based on the kilogram and the metre.

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A person standing a certain distance from an airplane with four equally noisy jet engines is experiencing a sound level of 145 d

Katyanochek1 [597]

Answer:

The sound level is 138.97 dB.

Explanation:

Given that,

Sound level L= 145 dB

We need to calculate the intensity

Using formula of sound intensity

$L=10\log(\dfrac{I}{I_{0}})$

Put the value into the formula

$145=10\log(\dfrac{I}{I_{0}})$

$\log(\dfrac{I}{I_{0}})=\dfrac{145}{10}$

$\log(\dfrac{I}{I_{0}})=14.5$

$\dfrac{I}{I_{0}}=10^{14.5}$

$I=10^{14.5}\times I_{0}$

$I=10^{14.5}\times10^{-12}$

$I=316.2$

We need to calculate the noise of one engine

Using formula of intensity

$I'=\dfrac{I}{4}$

Put the value into the formula

$I'=\dfrac{316.2}{4}$

$I'=79.05$

We need to calculate the intensity level due to one engine

Using formula of sound intensity

$L'=10\log(\dfrac{I'}{I_{0}})$

$L'=10\log(\dfrac{79.05}{10^{-12}})$

$L'=138.97\ dB$

Hence, The sound level is 138.97 dB

5 0

3 years ago

Your are on a boat on a lake with no current. The lake is full of sharks that will eat you if you put your hands too close to th

Drupady [299]

Answer:

throw the lakes to make a current maybe?

Explanation:

6 0

2 years ago

Which of the following is not a double-replacement?

zhannawk [14.2K]

Answer:

The correct answer is option D.

Explanation:

From the given options the reaction which is not a double replacement reaction is:

$Zn (s) + 2HCl (aq)\rightarrow H_2 (g) + ZnCl_2 (s)$

This because the above reaction is an example of single replacement reaction.

$AB+C\rightarrow AC+B$

Whereas;

Double replacement reaction is a type of chemical reaction in which exchange of ions among the reactants take place.

$AB+CD\rightarrow AD+CB$

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3 years ago

What is the mass of an object that requires 100N of force in order to accelerate it at 10m/s2 ?

Debora [2.8K]

Answer:

We know that f=ma

Rearranging

M=f÷a so m=10kg

Explanation:

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3 years ago

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If you travel 450 meters in 40 seconds, what is your average speed in meters per

Vedmedyk [2.9K]

Answer:

The answer is a 11.25m/s

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3 years ago

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