I need help with these two questions

Answer:

The age of the earliest known human-like footprints is approximately 3000000 years.

Explanation:

Decay of isotopes is represented by the following ordinary differential equation:

[tex]\frac{dm}{dt} = -\frac{m}{\tau}[/tex] (Eq. 1)

Where:

[tex]\frac{dm}{dt}[/tex] - First derivative of mass with respect to time, measured in miligrams per year.

[tex]m[/tex] - Current mass of the isotope, measured in miligrams.

[tex]\tau[/tex] - Time constant, measured in years.

Now we proceed to obtain the solution of the differential equation:

[tex]\int\limits {\frac{dm}{m} } = -\frac{1}{\tau}\int dt[/tex]

[tex]\ln m = -\frac{t}{\tau}+C[/tex]

[tex]m(t) = e^{-\frac{t}{\tau}+C }[/tex]

[tex]m(t) = m_{o}\cdot e^{-\frac{t}{\tau} }[/tex] (Eq. 2)

Where:

[tex]m_{o}[/tex] - Initial mass of the isotope, measured in miligrams.

[tex]t[/tex] - Time, measured in years.

[tex]\tau[/tex] - Time constant, measured in years.

We proceed to clear time within the formula presented above:

[tex]\ln \frac{m(t)}{m_{o}} = -\frac{t}{\tau}[/tex]

[tex]t = -\tau \cdot \ln \frac{m(t)}{m_{o}}[/tex]

In addition, time constant can be found as a function of half-life:

[tex]\tau = \frac{t_{1/2}}{\ln 2}[/tex] (Eq. 3)

If we know that [tex]t_{1/2} = 500000\,yr[/tex], [tex]m_{o} = 8\,mg[/tex] and [tex]m(t) = 0.125\,mg[/tex], the age of the earliest known human-like footprints is:

[tex]\tau = \frac{500000\,yr}{\ln 2}[/tex]

[tex]\tau \approx 721347.520\,yr[/tex]

[tex]t = -(721347.520\,yr)\cdot \ln \left(\frac{0.125\,mg}{8\,mg} \right)[/tex]

[tex]t \approx 3000000\,yr[/tex]

The age of the earliest known human-like footprints is approximately 3000000 years.

Answer:

Explanation:

The distance covered by an object given it's velocity and time taken can be found by using the formula

From the question

velocity = 35.0 mi/hr

time = 2455 s = 0.68 hr

We have

distance = 35 × 0.68

We have the final answer as

Hope this helps you

Answer:

C6H12O2

Explanation:

The first step in accurately deducing the structure/formula of the model is to count the number of carbon atoms, hydrogen atoms and oxygen atoms mentioned in the model. This gives the molecular formula of the compound.

Next, you look at there arrangement of atoms and bonds as stated in the model, this tells us the structure of the molecule and confirms the molecular formula initially deduced.

The structure of the compound is shown below.

Answer:

Your answer would be C6H12O2

Explanation: I hope I helped you :)

Answer:

Mg with 2 dots

Explanation:

Mg: as the valnce shell of Mg has 2 electrons only

presented by 2 dots

Answer:

'*:*'

Explanation:

I know this looks weird, but

'= electron

*:* equals the nucleus, so 2 protons and 2 neutrons

and then '=electron

Answer:

First One And Third Pls Mark Brainlest

Explanation:

Answer:

The uncertainty principle, proposed in 1927 by German physicist Werner Heisenberg, states that the more precisely a particle's position is measured, the less precisely its momentum can be known, and vice versa. ... They wanted to measure the polarization, or orientation, of the photon.

Answer:

Equation:

Q = m•C•ΔT

Answer:

Yes, Magnesium

Answer:D. 2857 joules

Explanation:

Not going to lie I guessed but got it right

According to specific heat capacity, 3596.208 joules of energy is required to heat 0.24 kg of lutetium from 296.2 K to 373.5 K.

Specific heat capacity is defined as the amount of energy required to raise the temperature of one gram of substance by one degree Celsius. It has units of calories or joules per gram per degree Celsius.

It varies with temperature and is different for each state of matter. Water in the liquid form has the highest specific heat capacity among all common substances .Specific heat capacity of a substance is infinite as it undergoes phase transition ,it is highest for gases and can rise if the gas is allowed to expand.

It is given by the formula ,

Q=mcΔT

Substitution in above formula gives, q= 0.24×154×97.3=3596.208 Joules.

Thus, 3596.208 joules of energy is required to heat 0.24 kg of lutetium from 296.2 K to 373.5 K.

Learn more about specific heat capacity,here:

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Answer:

E. A conductor is needed for electricity to flow in a circuit.

Explanation:

Electric current can flow without a resistor, as in short circuit.

A short circuit is an electrical circuit that allows a current to travel along an unintended path with no or very low electrical impedance.

Without a switch, electricity can flow in a circuit, switch is only used to close or open the circuit.

Thus, the only correct option is  E

E. A conductor is needed for electricity to flow in a circuit.

Answer:

3

Explanation:

3 ampers (it says in the problem)

Answer:

As the number of atoms in the reactants side is equal to the number of atoms in the product side, the reaction is balanced

Two hydrogen molecules per oxygen molecule are produced because water (H2O) has a ratio of two hydrogen atoms to one oxygen atom. A decomposition reaction occurs when one reactant breaks down into two or more products. This can be represented by the general equation: AB → A + B.

H2O is the chemical formula of water. It means that each molecule of water is made up of two hydrogen atoms, indicated by the letter H, and a single oxygen atom, represented by the letter O. Water is chemical substance with no smell, taste or color.

Answer:

Candle wax will melt to a liquid and burn as a gas. Only covalent compounds can be liquid or gas!

Explanation:

Question: Is Wax Ionic Or Covalent? - Ceramicsexpandusceramics.com

In the given question, wax is a covalent compound because it is composed of nonmetal atoms that share electrons to create covalent bonds.

Covalent compounds are formed when two or more nonmetal atoms share electrons in order to achieve a stable electron configuration.

Therefore, wax is a covalent compound because it is made up of non-metal atoms sharing electrons to form covalent bonds.

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The answer Is B;A chemical bond holds atoms together.

Answer:

I'm confused on what u need us to answer

Answer:

The answer is D, ductility

Explanation:

The definition of ductile is "(of a metal) able to be drawn out into a thin wire."

Number of Br atoms : 2.679 x 10²³

The mole is the number of particles contained in a substance

1 mol = 6.02.10²³

Moles can also be determined from the amount of substance mass and its molar mass

[tex]\tt mol=\dfrac{mass}{MW}[/tex]

Proust stated the Comparative Law that compounds are formed from elements with the same Mass Comparison so that the compound has a fixed composition of elements

[tex]\tt mass~Br=\dfrac{2.Ar~Br}{MW~CH_2Br_2}\times mass~CH_2Br_2\\\\mass~Br=\dfrac{2.80}{174}\times 38.7=35.59~g[/tex]

[tex]\tt \dfrac{35.59}{80}=0.445[/tex]

[tex]\tt 0.445\times 6.02\times 10^{23}=\boxed{\bold{2.679\times 10^{23}}}[/tex]

Answer: D. A 2 kg pot at 25C.

Explanation:

Answer:

He and Ar

Explanation:

Answer:

Stars generate energy through nuclear fusion. Here's an easy explanation about how the process works. ... Stars spend most of their lives repetitively compressing two hydrogen atoms into a single helium atom – plus a lot of energy, which is released as light and heat.

Answer:

By Newton's 2nd law, m*a=sum_of_forces where m is the mass and a the acceleration. Here there are two forces in opposed directions.

Thus 5*a=40-8=32 therefore a=32/5=6.4m^s/2

Answer:

Its going to be D) In sigma bonds the electrons are in the space between the joined atoms and pi bonds above and below the joined atoms

Answer:

158.17

Explanation:

divide the given mass by the molar mass

Answer:

Mg[tex]^+2[/tex]

Explanation:

Es el elemento que buscas.

Answer: A.En Hedu'Anna

Answer:

En Hedu’Anna!

Explanation:

Hope this is your answer i wasn't able to see he full question so i am not sure

Answer:

the core

Explanation:

Answer:

3rd option, the core.

Explanation:

Answer:Rubidium and Strontium

Explanation: