What are the rows on the periodic table called? What are the columns called? What do you know about elements in the same group?

I probably don't have to tell you that the other answer is nonsense, but I'll do it all the same, just in case... Half-life is defined as the time it takes for some radioactive substance to decay to half its original amount.

If it takes n half-lives for some substance with a starting amount of A to decay to a final amount of B, then

[tex]B = \dfrac{A}{2^n}[/tex]

1. If the half-life is x, then after 1 half-life, 5000 units of this substance decays to 2500 units. After another half-life, this decays to 1250. After another, this in turn decays to 625.

So 3 half-lives are required.

In terms of the equation above, we solve for n such that

[tex]625 = \dfrac{5000}{2^n} \implies 2^n = 8 \implies n=3[/tex]

since 2³ = 8.

2. Count how many times you halve 15,000 to end up with 3750:

15,000/2 = 7500

7500/2 = 3750

===>   2 half-lives

In other words,

[tex]3750 = \dfrac{15,000}{2^n} \implies 2^n = 4 \implies n=2[/tex]

3. After 1 half-life, you would end up with

12,000/2 = 6000

and after another half-life,

6000/2 = 3000

i.e.

[tex]\dfrac{12,000}{2^2} = \dfrac{12,000}4 = 3000[/tex]

4. After 1 half-life, you have

26,000/2 = 13,000

After 2 half-lives,

13,000/2 = 6500

After 3 half-lives,

6500/2 = 3250

After 4 half-lives,

3250/2 = 1625

i.e.

[tex]\dfrac{26,000}{2^4} = \dfrac{26,000}{16} = 1625[/tex]

5. If the half-life is 3 years, then 15 years = 3 half-lives.

In the last 3 years, 20,000 would have decayed to 10,000.

In the second-to-last 3 years, 40,000 would have decayed to 20,000.

In the first 3 years, 80,000 would have decayed to 40,000.

i.e.

[tex]\dfrac{x}{2^3} = 10,000 \implies x = 8\times10,000 = 80,000[/tex]

Answer:

Electrical

Explanation:

Electrical would be the energy that involves the flow of positive charges.

Answer: if every arrow=1m do 1 times 1 times 1 times 1

Explanation:

(p.s. it equals 1 meter in area 4 meters in perimeter)

Answer:

B Eight light-minutes

Explanation:

In the case when the distance separated earth and the sun so here we orbit the sun for a 150 million km distance and the light moves would be 300,000 kilometers per second

Now divide this

= 150 million ÷ 300,000 kilometers per second

= 500 seconds

This 500 seconds represent 8 minutes and 20 seconds

Hence, option B is correct

Answer:

B) Eight light-minutes

Answer:

Explanation:

Answer:

Element Symbol # of Atoms

Oxygen O 2

Sulfur S 1

Explanation:

Answer: b

Explanation:

p=mv

p=30

m=1500

rearrange to find v

(30)=(1500)(v)

v= 30/1500

v = 0.02 m/s

Answer:

it grows fast, spreads faster and kills off smaller native plants

Explanation:

honeysuckle spreads very quickly and blooms multiple times a year, spreading seeds and growing in more spots. everytime it does so, it cuts off other smaller native plants from the sunshine and kills them off

Answer:

bones

Explanation:

Bones are is preserved in cast and mold fossils.

Normally the other 'parts of the body' like muscles, ligaments, blood and organs are soft.

Answer:

bones

Explanation:

Answer:

hello your question is vague hence I will provide a general answer about what was known about atoms in the 19th Century

answer :

By the end of the 19th century more than half of the population believed in the presence of atoms and also in the 19th Century is was a known fact that atoms determine the chemical properties of an element

Explanation:

By the end of the 19th century more than half of the population believed in the presence of atoms and also by the 19th Century is was a known fact that atoms determine the chemical properties of an element.

John Dalton reintroduced the presence of atoms in 1800 with evidence which he used to develop atomic theory. with this theory people believed in the presence of atoms in nature and also that atoms determine the chemical properties of an element .

Answer: These ideas, that all men are created equal and that government is based on the consent of the governed, became the foundation for the US political ideal of popular sovereignty: that the government exists to serve the people, who elect representatives to express their will.

Explanation: Hope this helped! <3

Answer:

The correct answer is -

1. 67500 J

Explanation:

The formula for KE is  

K.  E.  =  1/ 2 *m v ^2  

So input the values we know:

K . E.  =  1/2 ⋅*150  *30 ^2

K . E.  =  150 * 900 /2

K . E . =  67500  

K . E.  = 67500

If the velocity is double then;

use 2v in the formula

K.  E.  = ( 1/ 2 )*m(2 v) ^2

= (1/2)*4m v ^2

it is four times to original Kinetic energy, and similarly if tripled then, it will be 9 times to original.

Answer:

1,2,3,4

Explanation:

Answer:

Photosynthesis occurs in the organelle, chloroplast .

Cellular respiration occurs in a plants or animals mitochondria.

Explanation:

Hope this helps! :)

Answer:

F(m)= mg(m)

m=F(m)/g(m)=72/1.6=45kg

F(e)= mg(e)= 45 x 10 m/s= 450N

Explanation:

potential energy =360800J

mass(m)=?

height (h)=25m

g=9.8m/s²

we have

potential energy =360800J

mgh=360800J

m×9.8×25=360800

m=360800/(9.8×25)=1472.653061kg

Answer:

HELP PLEASE!! GIVING BRAINLIEST!! If you answer this correctly ill answer some of your questions you have posted!

Answer: 2              1                  3  

is your answer

Explanation:

your'e welcome

Answer:

First one = 2

Second one = 1

Third one = 3

Explanation:

2       1      3

can i get brainliest I need it please

Answer:

Average speed = 5 m/s

Explanation:

Given the following data;

Distance = 100m

Time = 20 secs

To find the average speed;

Speed = distance/time

Substituting into the formula, we have;

Speed = 100/20

Speed = 5m/s

Therefore, Elsa's average speed is 5 meters per seconds.

air exert a pressure take a glass and put the water on it and small piece a paper and glass take downword and observe it so tha air exert pressure

Answer:

the answer would be conductors

Answer:

Kinetic energy increase

Answer:

increases

Explanation:

B,C,D maybe

Explanation:

plz dont get mad