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3 years ago

12

Why did scientists compare megalodons and great white sharks? SCIENCE

1 answer:

GenaCL600 [577]3 years ago

4 0

They have similar growth trajectories

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Determine the activity of the sample of cerium when the sample was 20 seconds old

Gre4nikov [31]

Answer:

There are $3.779\times 10^{23}$ atoms when the sample of cerium is 20 seconds old.

Explanation:

The decay of isotopes is modelled after the following exponential expression:

$N(t) = N_{o}\cdot e^{-\left(\frac{\ln 2}{t_{1/2}}\right)\cdot t }$ (1)

Where:

$N_{o}$ - Initial number of atoms, dimensionless.

$N(t)$ - Current number of atoms, dimensionless.

$t$ - Time, measured in seconds.

$t_{1/2}$ - Half-time, measured in seconds.

Now we clear the half-time within (1):

$\ln \frac{N(t)}{N_{o}} = -\frac{t\cdot \ln 2}{t_{1/2}}$

$t_{1/2} = -\frac{t\cdot \ln 2}{\ln \frac{N(t)}{N_{o}} }$

If we know that $N_{o} = 5\times 10^{23}$ , $N(t) = 2\times 10^{23}$ and $t = 66\,s$ , then the half-life of the isotope is:

$t_{1/2}=-\frac{(66\,s)\cdot \ln 2}{\ln \frac{2}{5} }$

$t_{1/2}\approx 49.927\,s$

And the decay equation for the sample is described by:

$N(t) = (5\times 10^{23})\cdot e^{-0.014\cdot t}$

Lastly, if we get that $t = 20\,s$ , then the activity of the sample of cerium is:

$N(20) = (5\times 10^{23})\cdot e^{(-0.014)\cdot (20)}$

$N (20) \approx 3.779\times 10^{23}$

There are $3.779\times 10^{23}$ atoms when the sample of cerium is 20 seconds old.

7 0

3 years ago

How many neutrons does an element have of its atomic number is 50 and its mass number is 156?

pshichka [43]

Ok so I think you would first subtract

156 - 50 = 106

Since atomic number is based on the number of protons, you should subtract the 50 from 156

106 should be your answer

Hope this helps!

3 0

3 years ago

Derive an approximate formula for the mutual inductance of two circular rings of the same radius a, arranged like wheels on the

son4ous [18]

Answer:

Please check the attached file for the derivation

Explanation:

Check the attached file

7 0

3 years ago

The average standard rectangular building brick has a mass of 3.10 kg and dimensions of 225 m x 112 m x 75 m. The gravitational

zzz [600]

Answer:

$P=3.61\times 10^{-3}\ Pa$

Explanation:

Given that,

Mass of a brick, m = 3.1 kg

The dimensions of the brick 225 m x 112 m x 75 m

We need to find the maximum pressure created by the brick. We know that, the force acting per unit area is called pressure exerted. It is given by the formula as follows :

$P=\dfrac{F}{A}$

F = mg

A = area with minimum dimensions i.e. 112 m x 75 m

Pressure is maximum when the area is least.

So,

$P=\dfrac{mg}{A}\\\\P=\dfrac{3.1\times 9.8}{112\times 75}\\\\P=3.61\times 10^{-3}\ Pa$

So, the maximum pressure created by brick is $3.61\times 10^{-3}\ Pa$ .

5 0

3 years ago

Listed in the Item Bank are some important labels for sections of the image below. To find out more information about labels, so

gizmo_the_mogwai [7]

Answer:reactant,active site,enzyme below,substrate,products

Explanation:

5 0

3 years ago