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4 years ago

Index fossils are used to determine the relative ages of rock and fossils and are also used to

1 answer:

3 0

Index fossils are used to determine the relative ages of rock and fossils and are also used to define the boundaries between geologic periods.

<u>Option: A</u>

<u>Explanation:</u>

The fossils which are recognized as fossils guides or indicator fossils are used to classify and recognize geological or faunal periods, termed as index fossils. It must be of short vertical reach, wide geographic distribution and swift patterns in evolution. It helps to assess the rock layers ' age and helps to date other fossils found close and around them. For an instance, Ammonites were abundant in the Mesozoic period between 245 to 65 mya, they have not been found after the Cretaceous era, as they became endangered during the K-T extinction (65 mya).

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Charge Q is distributed uniformly throughout the volume of an insulating sphere of radius R = 4.00 cm. At a distance of r = 8.00

Elena L [17]

Answer:

$2.62898\times 10^{-6}\ C/m^3$

$1979.99974\ N/C$

Explanation:

k = Coulomb constant = $8.99\times 10^{9}\ Nm^2/C^2$

Q = Charge

r = Distance = 8 cm

R = Radius = 4 cm

Electric field is given by

$E=\dfrac{kQ}{r^2}\\\Rightarrow Q=\dfrac{Er^2}{k}\\\Rightarrow E=\dfrac{990\times 0.08^2}{8.99\times 10^{9}}\\\Rightarrow Q=7.04783\times 10^{-10}\ C$

Volume charge density is given by

$\sigma=\dfrac{Q}{\dfrac{4}{3}\pi R^3}\\\Rightarrow \sigma=\dfrac{7.04783\times 10^{-10}}{\dfrac{4}{3}\pi (0.04)^3}\\\Rightarrow \sigma=2.62898\times 10^{-6}\ C/m^3$

The volume charge density for the sphere is $2.62898\times 10^{-6}\ C/m^3$

$E=\dfrac{kQr}{R^3}\\\Rightarrow E=\dfrac{8.99\times 10^9\times 7.04783\times 10^{-10}\times 0.02}{0.04^3}\\\Rightarrow E=1979.99974\ N/C$

The magnitude of the electric field is $1979.99974\ N/C$

8 0

3 years ago

An electron moving parallel to a uniform electric field increases its speed from 2.0 × 107 m/s to 4.0 × 107 m/s over a distance

jeka94

Answer:

$1.8\times 105 N/C$

Explanation:

We are given that

$u=2\times 10^7 m/s$

$v=4\times 10^7 m/s$

d=1.9 cm= $\frac{1.9}{100}=0.019 m$

Using 1m=100 cm

We have to find the electric field strength.

$v^2-u^2=2as$

Using the formula

$(4\times 10^7)^2-(2\times 10^7)^2=2a(0.019)$

$16\times 10^{14}-4\times 10^{14}=0.038a$

$0.038a=12\times 10^{14}$

$a=\frac{12}{0.038}\times 10^{14}=3.16\times 10^{16}m/s^2$

$q=1.6\times 10^{-19} C$

Mass of electron,m $=9.1\times 10^{-31} kg$

$E=\frac{ma}{q}$

Substitute the values

$E=\frac{9.1\times 10^{-31}\times 3.16\times 10^{16}}{1.6\times 10^{-19}}$

$E=1.8\times 105 N/C$

7 0

4 years ago

A container of soy milk has the instructions on its label to “shake well before opening ” The soy milk is most likely a ?

Elena-2011 [213]

Answer:

D. Suspension

4 0

3 years ago

A woman is 160160cm tall. What is the minimum vertical length of a mirror in which she can see her entire body while standing up

kipiarov [429]

This question is incomplete, the complete question is;

A woman is 160cm tall. What is the minimum vertical length of a mirror in which she can see her entire body while standing upright.

Hint: Consider the ray diagram below, of the rays that enable her to see her feet and the top of her head.

Use what you know about the law of reflection, together with a bit geometry.

The missing Image is uploaded along this answer below.

Answer:

the minimum vertical length of a mirror in which she can see her entire body while standing upright is 80 cm

Explanation:

Given the data in the question and illustrated in the image below,

From image 2;

The distance from the woman's eyes to the top of her head is represented as b and a represent the distance from her eyes to her feet.

Therefore, since her height is 160 cm

a + b = 160 ------ let this be equation 1

i.e AD + DG = 160 cm

Now, from the same image 2, we will notice that triangle ABC and tringle CBD are similar, so

∠ABC = ∠CBD

AC = CD

since AD = a and AC + CD = A

AC = CD = a/2

Also, triangle DEF and FEG are si,ilar

∠DEF = ∠FEG

DF = FG

since DG = b and DF + FG = b

DF = b/2

so the minimum vertical length of a mirror in which the woman can see her entire body while standing upright will be;

⇒ a/2 + b/2

⇒ a + b / 2

from equation 1, a + b = 160

⇒ a + b / 2 = 160 / 2 = 80

Therefore, the minimum vertical length of a mirror in which she can see her entire body while standing upright is 80 cm

4 0

3 years ago

Chemical changes occur as energy is transferred when molecules- - or - to form one or more new substances

timurjin [86]

Answer:

Correct options are C. As food is digested, molecule bonds are broken, allowing new molecules to form that can be used by our bodies.

D. Energy stored in organic fuels are used for heat and electricity/ When batteries are connected to a circuit, a reaction occurs inside the cell producing electrical energy.

Explanation:

The breakdown of food leads to the release of chemical energy which was first stored in food. This energy is used to drive necessary functions of the body. A series of chemical reactions are involved in the breakdown of food and changing them into useful components for the cell.

Chemical energy is stored in circuits. When the battery is connected to a circuit, the chemical energy gets transferred into electrical energy.

4 0

3 years ago

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