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3 years ago

True of false metals like copper are sometimes used to fill cavities in teeth

Physics

1 answer:

vovikov84 [41]3 years ago

4 0

Yes. Copper, mercury, and tin are all used to fill in cavities.

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Uranium-235 decays to thorium-231 with a half-life of 700 million years. When a rock was formed, it contained 6400 million urani

Dahasolnce [82]

Answer:

proof in explanation

Explanation:

First, we will calculate the number of half-lives:

$n = \frac{t}{t_{1/2}}$

where,

n = no. of half-lives = ?

t = total time passed = 2100 million years

$t_{1/2}$ = half-life = 700 million years

Therefore,

$n = \frac{2100\ million\ years}{700\ million\ years}\\\\n = 3$

Now, we will calculate the number of uranium nuclei left ( $n_u$ ):

$n_u = \frac{1}{2^{n} }(total\ nuclei)\\\\n_u = \frac{1}{2^{3} }(6400\ million)\\\\n_u = \frac{1}{8}(6400\ million)\\\\n_u = 800\ million$

and the rest of the uranium nuclei will become thorium nuclei ( $u_{th}$ )

$n_{th} = total\ nuclei - n_u\\n_{th} = 6400\ million-800\ million\\n_{th} = 5600\ million$

dividing both:

$\frac{n_{th}}{n_u}=\frac{5600\ million}{800\ million} \\\\n_{th} = 7n_u$

<u>Hence, it is proven that after 2100 million years there are seven times more thorium nuclei than uranium nuclei in the rock.</u>

6 0

3 years ago

Average human body temperature is 98.6°F. What is the equivalent in degrees Celsius?

Gala2k [10]

37° Celsius is equal to 98.6° Fahrenheit

6 0

3 years ago

12345 [234]

Answer:

charcoal is the correct answer

hope it helps , pls mark me as brainliest

6 0

3 years ago

An object has a 600 N force pushing it to the right, while a 700 N force pushes in the opposite direction. Gravity also acts on

nordsb [41]

Left is the answer 3

6 0

3 years ago

Read 2 more answers

The voltage ???? in a simple electrical circuit is slowly decreasing as the battery wears out. The resistance ???? is slowly inc

zimovet [89]

Answer:

The change in current at $R =456 \Omega$ is $\frac{dI}{dt} = 7.032 * 10^{-5} A/s$

Explanation:

From the question we are told that

The resistance is $R = 465 \Omega$

The current is $I = 0.09A$

The change in voltage with respect to time is $\frac{dV}{dt} = - 0.03 V/s$

The change in resistance with time is $\frac{dR}{dt} = 0.03 \Omega /s$

According to ohm's law

$V = IR$

differentiating with respect to time using chain rule

$\frac{dV}{dt} = I \frac{dR}{dt} + R * \frac{dI}{dt}$

substituting value at R = 456

$-0.0327 = 0.09 * 0.03 + 456* \frac{dI}{dt}$

$\frac{dI}{dt} = 7.032 * 10^{-5} A/s$

6 0

3 years ago