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Grace [21]
3 years ago
12

Two different radioactive isotopes decay to 10% of their respective original amounts. Isotope A does this in 33 days, while isot

ope B does this in 43 days. What is the approximate difference in the half-lives of the isotopes?
Mathematics
2 answers:
Maslowich3 years ago
6 0

Answer:

A. 3 Days

Step-by-step explanation:

Just took the test hope this helps :)

Andrews [41]3 years ago
4 0

Answer:

The approximate difference in the half-lives of the isotopes is 66 days.

Step-by-step explanation:

The decay of an isotope is represented by the following differential equation:

\frac{dm}{dt} = -\frac{t}{\tau}

Where:

m - Current mass of the isotope, measured in kilograms.

t - Time, measured in days.

\tau - Time constant, measured in days.

The solution of the differential equation is:

m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }

Where m_{o} is the initial mass of the isotope, measure in kilograms.

Now, the time constant is cleared:

\ln \frac{m(t)}{m_{o}} = -\frac{t}{\tau}

\tau = -\frac{t}{\ln \frac{m(t)}{m_{o}} }

The half-life of a isotope (t_{1/2}) as a function of time constant is:

t_{1/2} = \tau \cdot \ln2

t_{1/2} = -\left(\frac{t}{\ln\frac{m(t)}{m_{o}} }\right) \cdot \ln 2

The half-life difference between isotope B and isotope A is:

\Delta t_{1/2} = \left| -\left(\frac{t_{A}}{\ln \frac{m_{A}(t)}{m_{o,A}} } \right)\cdot \ln 2+\left(\frac{t_{B}}{\ln \frac{m_{B}(t)}{m_{o,B}} } \right)\cdot \ln 2\right|

If \frac{m_{A}(t)}{m_{o,A}} = \frac{m_{B}(t)}{m_{o,B}} = 0.9, t_{A} = 33\,days and t_{B} = 43\,days, the difference in the half-lives of the isotopes is:

\Delta t_{1/2} = \left|-\left(\frac{33\,days}{\ln 0.90} \right)\cdot \ln 2 + \left(\frac{43\,days}{\ln 0.90} \right)\cdot \ln 2\right|

\Delta t_{1/2} \approx 65.788\,days

The approximate difference in the half-lives of the isotopes is 66 days.

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joja [24]

a.

The y-coordinate of the vector with its terminal point in the second quadrant is 6.

The magnitude of the vector, r = √(x² + y²) where x = x-coorcinate of vector = -5 and y = y-coordinate of vector.

Since r = √61 and r = √(x² + y²)

Making y subject of the formula, we have

y = √(r² - x²)  

Substituting the values of the variables into the equation, we have

y = √((√61)² - (-5)²)  

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y = ±√36

y = ±6

Since r is in the second quadrant, its y-coordinate is positive.

So, y = 6

So, the y-coordinate of the vector with its terminal point in the second quadrant is 6.

b.

The direction angle of the vector with its terminal point in the second quadrant is 130°

The direction angle of the vector is gotten from tanФ = y/x

Subsstituting x and y into the equation, we have

tanФ = y/x

tanФ = 6/-5

tanФ = -1.2

tan(180° - Ф) = 1.2

Taking inverse tan of both sides, we have

180° - Ф = tan⁻¹(1.2)

180° - Ф = 50.2°

Ф = 180° - 50.2°

Ф = 129.8°

Ф ≅ 130° to the neares whole number

The direction angle of the vector with its terminal point in the second quadrant is 130°.

Learn more about vectors here:

brainly.com/question/18478651

3 0
2 years ago
The ratio of red cars to blue cars in a parking lot was 5:3. If there were 40 red <br> cars
Mars2501 [29]

Answer:

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5 0
3 years ago
A table is on sale for $289, which is 32% less than the regular price.
prohojiy [21]

Answer:

R = \$903.125

Step-by-step explanation:

Given

Selling\ Price = \$289

Rate = 32\%

Required

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From the question, we understand that:

R * 32\% = \$289

So, we have:

R * 0.32 = \$289

R = \frac{\$289}{0.32}

R = \$903.125

<em>Hence, the regular price is $903.125</em>

3 0
3 years ago
Which of the following is a point-slope equation of a line that passes through
Mademuasel [1]

Answer:

The Answer is: y = -2/3x + 10/3

Step-by-step explanation:

Given points (-1, 4) and (8, -2) first find the slope:

m = (y - y1)/(x - x1)

m = (4 - (-2)) / (-1 - 8)

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y = -2/3x + 16/3 - 2

y = -2/3x + 16/3 - 6/3

y = -2/3x + 10/3

Proof using the point (-1, 4):

f(-1) = -2/3(-1) + 10/3

= 2/3 + 10/3

= 12/3 = 4, giving point (-1, 4)

Hope this helps! Have an Awesome Day!! :-)

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alina1380 [7]

Answer:

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Step-by-step explanation:

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