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
garik1379 [7]
3 years ago
13

A radioactive substance decays according to the formula w = 20e¡kt grams where t is the time in hours. a find k given that after

50 hours the weight is 10 grams. b find the weight of radioactive substance present at: i t = 0 hours ii t = 24 hours iii t = 1 week. c how long will it take for the weight to reach 1 gram? d find the rate of radioactive decay at: i t = 100 hours ii t = 1000 hours. e show that dw dt is proportional to the weight of substance remaining.
Physics
1 answer:
blagie [28]3 years ago
5 0
W=20 e(-kt)  
A. Rearranging gives k= -(ln(w/20)/t 
 Substituting w= 10 and solving gives k=0.014 
 B. Using W=20e(-kt). After 0 hours, W=20. After 24 hours, W=14.29g. After 1 week (24x7=168h) W=1.9g 
 C. Rearranging gives t=-(ln(10/20)/k. Substituting w=1 and solving gives t=214 hours. 
 D. Differentiating gives dW/ dt = -20ke(-kt). Solving for t=100 gives dW/dt = 0.07g/h. Solving for t=1000 gives 0.0000002g/h 
 E. dW/dt = -20ke(-kt). But W=20e(-kt) so dW/dt = -kW
You might be interested in
The part of earth where all living things are found is called the
Amanda [17]

Answer:

Hey Dude....

Explanation:

This is ur answer.....

<em>The biosphere is made up of the parts of Earth where life exists. The biosphere extends from the deepest root systems of trees to the dark environment of ocean trenches, to lush rain forests and high mountaintops.</em>

Hope it helps!

Brainliest pls!

Follow me! :)

5 0
3 years ago
Which resistors in the circuit are connected in series?
Lisa [10]

Answer:

it's C and D... do you understand?

7 0
3 years ago
A particle makes 800 revolution in 4 minutes of a circle of 5cm. Find
vladimir1956 [14]

Answer:

i) The period of the particle is 0.3 seconds

ii) The angular velocity is approximately 20.94 rad/s

iii) The linear velocity is approximately 1.047 m/s

iv) The centripetal acceleration is approximately 6.98 m/s²

Explanation:

The given parameters are;

The number of revolution of the particle, n = 800 revolution

The time it takes the particle to make 800 revolutions = 4 minutes

The dimension of the circle = 5 cm = 0.05 m

Given that the dimension of the circle is the radius of the circle, we have;

i) The period of the particle, T = The time to complete one revolution

T = 1/(The number of revolutions per second)

∴ T = 1/(800 rev/(4 min × 60 s/min)) = 3/10 s

The period, T = 3/10 seconds = 0.3 seconds

ii) The angular velocity, ω = Angle covered/(Time)

800 revolutions in 4 minutes = Angle of (800 × 2·π) in 4 minutes

∴ ω = (800 × 2·π)/(4 × 60) = 20·π/3

The angular velocity, ω = 20·π/3 rad/s ≈ 20.94 rad/s

iii) The linear velocity, v = r × ω

∴ The linear velocity, v = 0.05 m × 20·π/3 rad/s = π/3 m/s ≈ 1.047 m/s

iv) The centripetal acceleration, a_c = v²/r

∴ The centripetal acceleration, a_c = (π/3)²/(0.05) = 20·π/9

The centripetal acceleration, a_c = 20·π/9 m/s² ≈ 6.98 m/s²

4 0
3 years ago
Sam receives the kicked football on the 3 yd line and runs straight ahead toward the goal line before cutting to the right at th
Pie

Answer:

Distance: 21 yd, displacement: 15 yd, gain in the play: 12 yd

Explanation:

The distance travelled by Sam is just the sum of the length of each part of Sam's motion, regardless of the direction. Initially, Sam run from the 3 yd line to the 15 yd line, so (15-3)=12 yd. Then, he run also 9 yd to the right. Therefore, the total distance is

d = 12 + 9 = 21 yd

The displacement instead is a vector connecting the starting point with the final point of the motion. Sam run first 12 yd straight ahead and then 9 yd to the right; these two motions are perpendicular to each other, so we can find the displacement simply by using Pythagorean's theorem:

d=\sqrt{12^2+9^2}=15 yd

Finally, the yards gained by Sam in the play are simply given by the distance covered along the forward-backward direction only. Since Sam only run from the 3 yd line to the 15 yd line along this direction, then the gain in this play was

d = 15 - 3 = 12 yd

7 0
3 years ago
How fast does water flow from a hole at the bottom of a very wide, 3.2 m deep storage tank filled with water
Nezavi [6.7K]

Answer:

the velocity of the water flow is 7.92 m/s

Explanation:

The computation of the velocity of the water flow is as follows

Here we use the Bernouli equation

As we know that

V_1 = \sqrt{2g(h_2 - h_1)}\\\\=\sqrt{2g(\Delta h)}  \\\\= \sqrt{2\times9.8\times3.2} \\\\= \sqrt{62.72}

= 7.92 m/s

Hence, the velocity of the water flow is 7.92 m/s

We simply applied the above formula so that the correct value could come

And, the same is to be considered

5 0
3 years ago
Other questions:
  • A car is traveling around a horizontal circular track with radius r = 210 m at a constant speed v = 23 m/s as shown. The angle θ
    14·1 answer
  • Explain what happens to the atoms in the reactants during a chemical reaction
    5·1 answer
  • Describe two rights and two responsibilities that you have as an employee
    5·2 answers
  • A sound wave has a frequency of 615 hz in air and a wavelength of 0.54 m. what is the temperature of the air? assume the velocit
    5·1 answer
  • A wave of amplitude 0.4 m interferes with a second wave of amplitude 0.23 m traveling in the same direction. What is the largest
    14·1 answer
  • A ship was traveling across the Atlantic Ocean. It traveled 2,000 kilometers at a rate of 40 kilometers per hour. How long did i
    14·1 answer
  • The _____ is the process scientists use to conduct research, which includes a continuing cycle of exploration, critical thinking
    13·2 answers
  • - Which force is generally stronger?
    10·1 answer
  • (a) Calculate the height of a cliff if it takes 2. 35 s for a rock to hit the ground when it is thrown straight up from the clif
    12·1 answer
  • A soccer ball is kicked from the top of one building with a height of H1 = 30.2 m to another building with a height of H2 = 12.0
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!