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natta225 [31]
3 years ago
6

Each time you dumped the pennies, one half-life passed; it has been shown that the half-life for this radioactive isotope is 20

years
In the year 2000, an archaeology team unearths pottery and is using this isotope for radiometric dating to place the age of the pottery
It is shown that 95% of the nuclei have decayed
Approximately how long ago was the pottery made?
Physics
1 answer:
tresset_1 [31]3 years ago
3 0
The exponential decay function is shown as:

At = Ao*2^(-t/h)

Where:

At = Final amount
Ao = original amount
t = time
h = years for half-life to occur

We are not given the original and final amounts, but we are told that after the certain amount of time had passed, only 5% had remained. So if we were to isolate At and Ao in one side of the equation, such that: At/Ao = 0.05, we can solve for the missing variable, which is t.

Substituting:

<span>At/Ao = 2^(-t/h)
</span>0.05 = <span>2^(-t/20)
t = 86.44 years

Therefore, the pottery was made approximately 86.44 years ago.</span>
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What is the form of energy that is produced in all energy transformations?
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Answer: Long Answer...

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3 years ago
Two workers are sliding 300 kg crate across the floor. One worker pushes forward on the crate with a force of 400 N while the ot
almond37 [142]

Answer:

The kinetic coefficient of friction of the crate is 0.235.

Explanation:

As a first step, we need to construct a free body diagram for the crate, which is included below as attachment. Let supposed that forces exerted on the crate by both workers are in the positive direction. According to the Newton's First Law, a body is unable to change its state of motion when it is at rest or moves uniformly (at constant velocity). In consequence, magnitud of friction force must be equal to the sum of the two external forces. The equations of equilibrium of the crate are:

\Sigma F_{x} = P+T-\mu_{k}\cdot N = 0 (Ec. 1)

\Sigma F_{y} = N - W = 0 (Ec. 2)

Where:

P - Pushing force, measured in newtons.

T - Tension, measured in newtons.

\mu_{k} - Coefficient of kinetic friction, dimensionless.

N - Normal force, measured in newtons.

W - Weight of the crate, measured in newtons.

The system of equations is now reduced by algebraic means:

P+T -\mu_{k}\cdot W = 0

And we finally clear the coefficient of kinetic friction and apply the definition of weight:

\mu_{k} =\frac{P+T}{m\cdot g}

If we know that P = 400\,N, T = 290\,N, m = 300\,kg and g = 9.807\,\frac{m}{s^{2}}, then:

\mu_{k} = \frac{400\,N+290\,N}{(300\,kg)\cdot \left(9.807\,\frac{m}{s^{2}} \right)}

\mu_{k} = 0.235

The kinetic coefficient of friction of the crate is 0.235.

5 0
3 years ago
Lasers can be constructed that produce an extremely high intensity electromagnetic wave for a brief time—called pulsed lasers. T
alex41 [277]

Answer:

30643 J

Explanation:

\mu_0 = Vacuum permeability = 4\pi \times 10^{-7}\ H/m

t = Time taken = 1 ns

c = Speed of light = 3\times 10^8\ m/s

E_0 = Maximum electric field strength = 1.52\times 10^{11}\ V/m

A = Area = 1\ mm^2

Magnitude of magnetic field is given by

B_0=\dfrac{E_0}{c}\\\Rightarrow B_0=\dfrac{1.52\times 10^{11}}{3\times 10^8}\\\Rightarrow B_0=506.67\ T

Intensity is given by

I=\dfrac{cB_0^2}{2\mu_0}\\\Rightarrow I=\dfrac{3\times 10^8\times 506.67^2}{2\times 4\pi \times 10^{-7}}\\\Rightarrow I=3.0643\times 10^{19}\ W/m^2

Power, intensity and time have the relation

E=IAt\\\Rightarrow E=3.0643\times 10^{19}\times 1\times 10^{-6}\times 1\times 10^{-9}\\\Rightarrow E=30643\ J

The energy it delivers is 30643 J

4 0
3 years ago
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