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m_a_m_a [10]
3 years ago
7

A rock has 12.5 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion yea

rs. How long ago was the rock formed?
a) 1.25 billion years ago

b) 2.5 billion years ago

c) 3.75 billion years ago

d) 5 billion years ago
Chemistry
2 answers:
igor_vitrenko [27]3 years ago
7 0
A rock has 12.5 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion years. <span>3.75 billion years ago</span> was the <span>rock formed. the answer is letter C</span>
mylen [45]3 years ago
6 0

Answer:

the answer is b) 2.5 billion years.  if its half life is 1.25 billion years and there is only 25% of the element remaining, you would take 1.25 billion and multiply it by two to get 2.5 billion.

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If an object that stands 3 centimeters high is placed 12 centimeters in front of a plane mirror, how far from the mirror is the
ryzh [129]

Answer:

the mirror is 12 cm away from the image

Explanation:

; the image will be virtual and it will form at 12 cm distance behind the mirror.

7 0
3 years ago
Why is this image a good model for the Law of Conservation of Mass?
ZanzabumX [31]

Answer:

The Law of Conservation of Mass states that mass is neither created nor destroyed in chemical reactions. Since the number and type of atoms in the reactant side of the chemical equation are the same as on the product side, the Law of Conservation of Mass has been demonstrated.

Explanation:

In the answer.

8 0
3 years ago
Find the work done using data from the PV plot for an isothermal system.
Eduardwww [97]

Answer:

W = - 500 KJ

∴ the work is done on the system

Explanation:

isothermal system:

∴ ΔU = 0; ⇒ Q = W

∴ W = P1V1 -P2V2

⇒ W = ((100KPa)*(25m³)) - ((300KPa)*(10m³))

⇒ W = 2500KPa.m³ - 3000KPa,m³

⇒ W = - 500 KPa.m³ = - 500 KJ

∴ W (-) the work is done on the system

8 0
3 years ago
Steve walks from his house 5 I'm south then turns east and walks 2 km. Then he walks 9 in North to his older sister's house. She
IgorLugansk [536]

Answer:

18 km

Explanation:

To know the distance, you need to be clear in the concept of distance.

According to the physics, the distance is a measurement that refers to the fact of how much an object has move from one point to another.

In this case, we have a person named Steve and he's walking through several points.

To calculate the distance that he moved, you just need to sum all the values of distance. In this case, it's not neccesary to do calculations regarding the components of the x or y axis, because we are not talking about displacement, where it actually counts. But in this case, we just need all the covered distance that Steven walked since the beggining.

So, no more talk, let's do calculations:

D = 5 + 2 + 9 + 2 = 18 km

So the final answer would be:

<h2>Distance = 18 km</h2>

Hope this helps

5 0
3 years ago
Write 2,469,100 in Engineering Notation with 3 significant figures.
Gala2k [10]

Answer: 2.47\times 10^{6}

Explanation:

Engineering notation : It is the representation of expressing the numbers that are too big or too small and are represented in the decimal form times 10 raise to the power.  It is similar to the scientific notation but in engineering notation, the powers of ten are always multiples of 3.

The engineering notation written in the form:

a\times 10^b

where,

a = the number which is greater than 0 and less than 999

b = an integer multiple of 3

Now converting the given value of 2,469,100 into engineering notation, we get 2.47\times 10^{6}

Hence, the correct answer is, 2.47\times 10^{6}

6 0
3 years ago
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