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SpyIntel [72]
3 years ago
7

The half-life of a certain element is 100 days. How many half-lives will it be before only one-eighth of this element remains?

Physics
1 answer:
Natalka [10]3 years ago
7 0

Answer:

3

Explanation:

The half-life is the time it takes for the amount of radioactive isotope to halve. Therefore, we have:

- After 1 half-life, only 1/2 of the element will be left

- After 2 half-lives, only 1/4 of the element will be left

- After 3 half-lives, only 1/8 of the element will be left

So, it will take 3 half-lives for the element to become 1/8 of its original amount.

Mathematically, this can be also verified by using the equation

\frac{N(t)}{N_0}=(\frac{1}{2})^\frac{t}{\tau_{1/2}}

where

N(t) is the amount of the element left at time t

N0 is the initial amount of the element

\tau_{1/2} is the half-life

Substituting t=3\tau_{1/2} (3 half-lives), we find

\frac{N(t)}{N_0}=(\frac{1}{2})^3=\frac{1}{8}

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A satellite orbits at a distance from the Earth's center of about 2.60 Earth radii and takes 5.89 hours to go around once. What
Elenna [48]

Answer:

424088766.068 m

Explanation:

Radius of the circular orbit that the satellite is 2.6 Earth radii (r) = 2.6 R

R = Radius of earth = 6371000 m (mean radius)

In order to find the distance that the satellite travels in 5.89 hours to complete one complete revolution is the circumference of the circular orbit

Circumference of a circle = 2×π×r

⇒Distance travelled in 5.89 hours = 2×π×2.6 R

⇒Distance travelled in 5.89 hours = 2×π×2.6×6371000

⇒Distance travelled in 5.89 hours = 104078451.3393m

Distance travelled in 1 hour = 104078451.3393/5.89 = 17670365.252 m

∴ Distance travelled in 24 hours = 17670365.252×24 = 424088766.068 m

5 0
3 years ago
A radioactive isotope of the element potassium decays to produce argon. If the ratio of argon to potassium is found to be 31:1,
iris [78.8K]

Answer:

Explanation:

Argon to potassium ratio after 1 half life = 1:1

After 2 half lives = 75/25= 3:1

After 3 half lives = 87.5/12.5= 7:1

After 4 half lives = 93.75/6.25 = 15:1

After 5 half lives = 96.875/3.125 = 31/1

8 0
3 years ago
You’ve had practice calculating the grams of hydrogen gas, but it is also possible to calculate the amount of oxygen gas produce
alekssr [168]

Answer:41.991ml

Explanation:

Equations: 2 H2O → 4H+ + 4e + O2 OXIDATION

2 H+ + 2e → H2 REDUCTION 

Electrolysis is the chemical decomposition of compounds when electricity is made to pass through a molten compound or solution.

from the oxidation reaction:

1moles of oxygen requires 4moles of electrons to be discharged at the product

F=96500C/mol

Quantity of charge Q=It

=60*60*0.201A

Q=723.6C

Mole=Q/(F*mole ratio of electron)

Mole= 723.6/(4*96500)

Mole=((1809)/(965000))

M=0.0018746114

M1/M2=V1/V2

1/0.00187=22.4dm^3/V2

V2=22.4*0.00187

V2=0.04199129534dm^3

41.99129534ml

5 0
2 years ago
Evaluate ( 64800 ms ) 2 to three significant figures and express the answer in Si units. Express your answer using three signifi
Sergeu [11.5K]

Answer:

42.0×10² second²

Explanation:

Here, time is given in milisecond

(64800 ms)²

= 4199040000 ms²

The SI unit is seconds

1 second = 1000 milisecond

1\ milisecond=\frac{1}{1000}\ second

\\\Rightarrow 1\ milisecond^2=\left(\frac{1}{1000}\right)^2\ second^2

4199040000\ ms^2=4199040000\times \left(\frac{1}{1000}\right)^2\ second^2=4199.04\ second^2

42.0×10² second²

6 0
3 years ago
1. An object in free fall will have an initial velocity equal to zero when: a. It is thrown vertically down
Ne4ueva [31]

Answer:

b. It is dropped

Explanation:

If the initial velocity is zero, the object move from rest. That happens if the object is dropped

6 0
3 years ago
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