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Oksi-84 [34.3K]
2 years ago
6

A 75 lb (34 kg) boy falls out of a tree from a height of 10 ft (3 m). i. What is the kinetic energy of the boy when he hits the

ground? Round your answer to the nearest joule. ii. What is the speed of the boy when he hits the ground? Round your answer to two significant figures. iii. Using the conversion factors of 1 m = 1.094 yd and 1 mi = 1760 yd, calculate the speed of the boy in miles per hour when he hits the ground.
Chemistry
1 answer:
Jobisdone [24]2 years ago
4 0

Answer:

Kinetic energy of boy just before hitting the ground is \approx1000 J.

Speed of boy just before hitting the ground is 7.67 m/s

or 17.16 mi/hr.

Explanation:

Given that:

Mass of boy = 75lb = 34 kg

Height, h = 10ft = 3m

To find:

Kinetic energy of boy when he hits the ground.

<em>As per law of conservation of energy The potential energy gets converted to kinetic energy.</em>

<em></em>

<em></em>\therefore<em> </em>Kinetic energy at the time boy hits the ground = Initial potential energy of the boy when he was at the Height 'h'

The formula for potential energy is given as:

PE = mgh

Where m is the mass

g is the acceleration due to gravity, g = 9.8 m/s^2

h is the height of object

Putting all the values:

PE = 34 \times 9.8 \times 3 \approx 1000\ J

Hence, Kinetic energy is \approx1000 J.

Formula for Kinetic energy is:

KE = \dfrac{1}{2}mv^2

where m is the mass and

v is the speed

Putting the values and finding v:

1000 = \dfrac{1}{2}\times 34 \times v^2\\\Rightarrow v^2 = 58.82\\\Rightarrow v = 7.67\ m/s

Given that:

1 m = 1.094 yd and 1 mi = 1760 yd

\Rightarrow 1609\ m = 1\ mi

Converting 7.67 m/s to miles/hour:

\dfrac{7.67 \times 3600}{1609}=17.16\ mi/h

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Alveolar air (a mixture of nitrogen, oxygen, and carbon dioxide) has a total pressure of 0.998 atm. If the partial pressure of o
inn [45]

Answer:

The partial pressure of carbon dioxide is 22.8 mmHg

Explanation:

Dalton's Law is a gas law that relates the partial pressures of the gases in a mixture. This law says that the pressure of a gas mixture is equal to the sum of the partial pressures of all the gases present.

In this case:

Ptotal=Pnitrogen + Poxygen + Pcarbondioxide

You know that:

  • Ptotal= 0.998 atm
  • Pnitrogen= 0.770 atm
  • Poxygen= 0.198 atm
  • Pcarbondioxide= ?

Replacing:

0.998 atm=0.770 atm + 0.198 atm + Pcarbondioxide

Solving:

Pcarbondioxide= 0.998 atm - 0.770 atm - 0.198 atm

Pcarbondioxide= 0.03 atm

Now you apply the following rule of three: if 1 atm equals 760 mmHg, 0.03 atm how many mmHg equals?

Pcarbondioxide=\frac{0.03 atm*760 mmHg}{1 atm}

Pcarbondioxide= 22.8 mmHg

<u><em>The partial pressure of carbon dioxide is 22.8 mmHg</em></u>

6 0
2 years ago
Give four different chemical meanings for the word element and an example of each
Naddika [18.5K]

Answer ;

-An element is a substance containing only one type of atom, for example; H2 or 02  (consisting of atoms that all have the same number of protons).

-Microscopic, single atom of that element

-Macroscopic, sample of that element large enough to weigh on a balance

- A substance that cannot be broken down chemically; e.g; sodium metal,

Explanation;

-An element is a substance whose atoms all have the same number of protons: another way of saying this is that all of a particular element's atoms have the same atomic number. Elements are chemically the simplest substances and hence cannot be broken down using chemical reactions.

-An element is uniquely determined by the number of protons in the nuclei of its atoms.

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2 years ago
Which postulate of Dalton's theory is consistent with the following observation concerning the weights of reactants and products
hram777 [196]

<u>Answer:</u> This illustrates law of conservation of mass.

<u>Explanation:</u>

Dalton's theory is based on mainly two laws which are law of conservation of mass and law of constant proportion.

Law of conservation of mass states that mass can neither be created nor be destroyed but it can only be transformed from one form to another form.

This also means that total mass on the reactant side must be equal to the total mass on the product side.

The chemical equation for the decomposition of calcium carbonate follows:

CaCO_3\rightarrow CaO+CO_2

We are given:

Mass of calcium carbonate = 100 grams

Mass of calcium oxide = 56 grams

Mass of carbon dioxide = 44 grams

Total mass on reactant side = 100  g

Total mass on product side = 56 + 44 = 100 g

As, the total mass on reactant side is equal to the total mass on product side.

Thus, this illustrates law of conservation of mass.

6 0
2 years ago
Which of the following compounds has polar covalent bonds: NaBr, Br2, HBr, and CBr4?
svetlana [45]

Answer: Option (e) is the correct answer.

Explanation:

A bond that is formed when an electron is transferred from one atom to another results in the formation of an ionic bond.

For example, NaBr will be an ionic compound as there is transfer of electron from Na to Br.

Whereas a bond that is formed by sharing of electrons is known as a covalent bond.

For example, CBr_{4} will be a covalent compound as there is sharing of electron between carbon and bromine atom.

Also, when electrons are shared between the combining atoms and there is large difference in electronegativity of these atoms then partial charges develop on these atoms. As a result, it forms a polar covalent bond.

For example, in a HBr compound there is sharing of electrons between H and Br. Also, due to difference in electronegativity there will be partial positive charge on H and partial negative charge on Br.  

Thus, we can conclude that out of the given options HBr is the only compound that has polar covalent bonds.

8 0
2 years ago
For the reaction below, Kp 5 1.16 at 800.8C. CaCO3(s) 34 CaO(s) 1 CO2(g) If a 20.0-g sample of CaCO3 is put into a 10.0-L contai
Elena L [17]

Answer:

The mass percentage of calcium carbonated reacted is 2.5%.

Explanation:

The reaction is:

CaCO_{3}(s)--->CaO(s)+CO_{2}(g)

Thus the Kp of the equilibrium will be:

Kp = partial pressure of carbon dioxide [as the other are solid]

Moles of calcium carbonate initially present = \frac{mass}{molarmass}=\frac{20}{100}=0.2

Let us apply ICE table to the equilibrium given:

                        CaCO_{3}(s)--->CaO(s)+CO_{2}(g)

Initial                       0.2                       0          0

Change                 -x                            +x        +x

Equilibrium           0.2-x                         x          x

Kp = partial pressure of carbon dioxide

Kp = Kc(RT)ⁿ

where n = difference in the number of moles of gaseous products and reactants

for given reaction n = 1

R = gas constant = 8.314 J /mol K

T = temperature = 800 ⁰C = 1073 K

Putting values

Kc =\frac{Kp}{RT}=\frac{1.16}{8.314X1073}=1.3X10^{-4}

Kc = \frac{[CO_{2}][CaO]}{[CaCO_{3}]}= \frac{x^{2} }{(0.2-x)}=1.3X10^{-4}

1.3X10^{-4}(0.2-x)=x^{2}

x^{2} = 0.26X10^{-4}-1.3X10^{-4}x

On calculating

x =  0.005

where x = the moles of calcium carbonate dissociated or reacted.

Percentage of the moles or mass reacted = \frac{molesreacted X100}{initialmoles}=\frac{0.005X100}{0.2}=2.5%

7 0
2 years ago
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