1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
Vinvika [58]
2 years ago
7

Smoke detectors fall into two major classes. Ionization detectors, the most common units, contain two parallel electrodes that a

re typically separated by 3 cm with a 5-V potential difference across them. The air molecules between the electrodes are ionized by collisions with helium nuclei that are produced by a radioactive source. Most units are initially fueled with 60 million nuclei of radioactive americium 241 (half-life 430 years). The now-ionized air molecules drift toward one of the electrodes with an average speed of 0.1 m/s and thus support a small current between the two electrodes. Smoke particles that enter and combine with the ions reduce the current and initiate an alarm.
Photoelectric detectors, by contrast, contain a light-emitting diode that sends a beam of unpolarized light across a small chamber. The light beam usually has a wavelength of 6.0 × 10–7m and has an intensity of 1.0 × 10–3 W. When smoke particles enter the chamber, the light scatters in all directions. A photocell then senses either the increase in the scattered light or the reduced intensity of the light beam and sets off the alarm. The speed of light in air is 3.0 × 108 m/s.
Ionization detectors respond faster to the large smoke particles of flaming fires; photoelectric detectors sense the small particles of smoldering fires more quickly. Modern units have both types of detectors.
When fewer than 3.75 × 106 americium nuclei remain, the ionization smoke detector will not operate due to insufficient ionization. How much time will pass before there are this many nuclei remaining?
a. 1720 years
b. 2150 years
c. 4300 years
d. 6880 years
Physics
1 answer:
bonufazy [111]2 years ago
7 0

Answer:

1720 years is the amount of time that will pass.

Option a) 1720 years is the correct answer

Explanation:

Given the data in the question;

 Number of nuclei initially N₀  = 60 million = 60,000,000

After time t, Number of nuclei remaining N_{rem = 3.75 × 10⁶

Also given that; half-life of radioactive americium t_{1/2 = 430 years.

so;

λ = ln2 / t_{1/2

we substitute

λ = ln2 / 430 years

N_{rem = N₀e^(-λt)

solve for t

t = 1/λ × ln( N₀/N_{rem  )

so we substitute

t = 1 / (ln2 / 430 years) × ln( 60,000,000 / ( 3.75 × 10⁶ ) )

t = ( 430 years / ln2 ) × ln( 60,000,000 / ( 3.75 × 10⁶ ) )

t = ( 430 years / 0.693147 ) × ln( 16 )

t = 620.359 years × 2.7725887

t =  1720.0003 ≈ 1720 years

Therefore, 1720 years is the amount of time that will pass.

Option a) 1720 years is the correct answer

You might be interested in
Which material would you take, steel or bricks to design a bridge? Why?
Vesna [10]

Answer:

steel

Explanation:

steel because steel has more power to hold something up, where bricks arent as stable

4 0
2 years ago
Read 2 more answers
A boy pulls a 28.0-kg box with a 230-N force at 35° above a horizontal surface. If the coefficient of kinetic friction between t
ddd [48]

Answer:

1977.696 J

Explanation:

Given;

Weight of the box = 28.0 kg

Force applied by the boy = 230 N

angle between the horizontal and the force = 35°

Therefore,

the horizontal component of the force = 230 × cosθ

= 230 × cos 35°

= 188.405 N

Coefficient of kinetic friction, μ = 0.24

Force by friction, f = μN

here,

N = Normal force = Mass × acceleration due to gravity

or

N = 28 × 9.81 = 274.68 N

therefore,

f = 0.24 × 274.68

or

f = 65.9232 N

Now,

work done by the boy, W₁ = 188.405 N × Displacement  

= 188.405 N × 30

= 5652.15 J

and,

the

work done by the friction, W₂ = - 65.9232 N × Displacement  

= - 65.9232 N × 30 m

= - 1977.696 J

[ since the friction force acts opposite to the direction of motion, therefore the workdone will be negative]

8 0
3 years ago
un resorte de 10cm de longitud recibe una magnitud de fuerza que lo estira hasta medir 15cm ¿cual es la magnitud de la tension u
Ber [7]

Answer: 0.5

Explanation:

The modulus of elasticity (called <em>"alargamiento unitario"</em> in spanish) \epsilon of a spring is given by the following formula:

\epsilon=\frac{\Delta L}{L}

Where:

L=10 cm  is the original length of the spring

\Delta L=L_{f}-L  is the elongation of the spring, being L_{f}=15 cm the length of the spring after a force is applied to it.

\epsilon=\frac{L_{f}-L}{L}=\frac{15 cm - 10 cm}{10 cm}

Then:

\epsilon=0.5

8 0
3 years ago
What is the definition of gravity in simple terms?
Tema [17]

Answer:

Gravity, also called gravitation, in mechanics, the universal force of attraction acting between all matter. ... On Earth all bodies have a weight, or downward force of gravity, proportional to their mass, which Earth's mass exerts on them. Gravity is measured by the acceleration that it gives to freely falling objects

1 : A force of attraction that tends to draw particles or bodies together.

2 : The attraction of bodies by the force of gravity toward the center of the earth.

3 : Great seriousness.

3 0
3 years ago
A 100 kg bungee jumper leaps from a bridge. The bungee cord has an un-streched equilibrium length of 10 m, and a spring constant
nika2105 [10]

Answer:

11.78meters

Explanation:

Given data

Mass m = 100kg

Length of cord= 10m

Spring constant k= 35N/m

At the greatest vertical distance, the spring potential energy is equal to the gravitational potential energy

That is

Us=Ug

Us= 1/2kx^2

Ug= mgh

1/2kx^2= mgh

0.5*35*10^2= 100*9.81*h

0.5*35*100=981h

1750=981h

h= 1750/981

h= 1.78

Hence the bungee jumper will reach 1.78+10= 11.78meters below the surface of the bridge

6 0
3 years ago
Read 2 more answers
Other questions:
  • A 160 g basketball has a 32.7 cm diameter and may be approximated as a thin spherical shell. Starting from rest, how long will i
    12·1 answer
  • A sinusoidal wave is traveling on a string with speed 40 cm/s. The displacement of the particles of the string at x = 10 cm vari
    10·2 answers
  • If you increase the resistance in a series circuit, ________________
    5·1 answer
  • Explain why the life cycle of a star can be compared to the life style of a human
    11·1 answer
  • If two waves with identical crests and troughs meet, what is happening? The wave is reflecting. Constructive interference is occ
    9·2 answers
  • Two conducting spheres are each given a charge Q. The radius of the larger sphere is three times greater than that of the smalle
    13·1 answer
  • Help Me Please<br>8th grade science, one question ​
    14·1 answer
  • A cyclist covers the first part of her journey
    11·1 answer
  • Hello people ~
    8·1 answer
  • the curiosity rover sent to explore the surface of mars has an electric generator powered by heat from the radioactive decay of
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!