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
slamgirl [31]
3 years ago
5

How long will it take for a radioactive isotope with a decay constant of 0.15 (which means a half life of 4.6 days ) to decay to

5% of its original value?
Physics
1 answer:
jek_recluse [69]3 years ago
6 0
Radioactive decay is given by:
N = No x e^(-λt)
We know that N/No has to be 0.05
λ = 0.15
0.05 = e^(-0.15t)
t = ln(0.05)/(-0.15)
t = 19.97 days
You might be interested in
Steam is to be condensed on the shell side of a heat exchanger at 150 oF. Cooling water enters the tubes at 60 oF at a rate of 4
zalisa [80]

Answer:

a. 572Btu/s

b.0.1483Btu/s.R

Explanation:

a.Assume a steady state operation, KE and PE are both neglected and fluids properties are constant.

From table A-3E, the specific heat of water is c_p=1.0\ Btu/lbm.F, and the steam properties as, A-4E:

h_{fg}=1007.8Btu/lbm, s_{fg}=1.6529Btu/lbm.R

Using the energy balance for the system:

\dot E_{in}-\dot E_{out}=\bigtriangleup \dot E_{sys}=0\\\\\dot E_{in}=\dot E_{out}\\\\\dot Q_{in}+\dot m_{cw}h_1=\dot m_{cw}h_2\\\\\dot Q_{in}=\dot m_{cw}c_p(T_{out}-T_{in})\\\\\dot Q_{in}=44\times 1.0\times (73-60)=572\ Btu/s

Hence, the rate of heat transfer in the heat exchanger is 572Btu/s

b. Heat gained by the water is equal to the heat lost by the condensing steam.

-The rate of steam condensation is expressed as:

\dot m_{steam}=\frac{\dot Q}{h_{fg}}\\\\\dot m_{steam}=\frac{572}{1007.8}=0.5676lbm/s

Entropy generation in the heat exchanger could be defined using the entropy balance on the system:

\dot S_{in}-\dot S_{out}+\dot S_{gen}=\bigtriangleup \dot S_{sys}\\\\\dot m_1s_1+\dot m_3s_3-\dot m_2s_2-\dot m_4s_4+\dot S_{gen}=0\\\\\dot m_ws_1+\dot m_ss_3-\dot m_ws_2-\dot m_ss_4+\dot S_{gen}=0\\\\\dot S_{gen}=\dot m_w(s_2-s_1)+\dot m_s(s_4-s_3)\\\\\dot S_{gen}=\dot m c_p \ In(\frac{T_2}{T_1})-\dot m_ss_{fg}\\\\\\\dot S_{gen}=4.4\times 1.0\times \ In( {73+460)/(60+460)}-0.5676\times 1.6529\\\\=0.1483\ Btu/s.R

Hence,the rate of entropy generation in the heat exchanger. is 0.1483Btu/s.R

4 0
3 years ago
Which of the following is NOT a mental process?
sergij07 [2.7K]

Answer:

Its A. Walking on the beach

4 0
3 years ago
Read 2 more answers
What is the smallest possible piece an element in broken down into my normal laboratory processes
lozanna [386]

answer would be: A. atom

8 0
3 years ago
Mike is a runner. Mike runs 200m in 25s; what is his average velocity during the run? assume that units are in m/s. (asap, will
maw [93]
Velocity is displacement/time
(Displacement is the overall change in distance)

So you’ll want to divide 200 by 25, which should give you:

8 m/s

5 0
3 years ago
A container is filled to a depth of 19.0 cm with water. On top of the water floats a 31.0-cm-thick layer of oil with specific gr
IceJOKER [234]

Answer:

Absolute pressure of the oil will be 102822.8 Pa  

Explanation:

We have given height h = 31 cm = 0.31 m

Acceleration due to gravity g=9.8m/sec^2

Specific gravity of oil = 0.600

So density of oil \rho =0.6\times 1000=600kg/m^3

We know that absolute pressure is given by P=P_0+\rho gh, here P_0=1.01\times 10^5Pa

So absolute pressure will be equal to P=1.01\times 10^5+600\times 9.8\times 0.31=102822.8Pa

So absolute pressure of the oil will be 102822.8 Pa

6 0
3 years ago
Other questions:
  • What are two ways that convention currents in the ocean distribute the suns energy?
    14·1 answer
  • What should be the spring constant k of a spring designed to bring a 1200 kg car to rest from a speed of 85 km/h so that the occ
    12·1 answer
  • Most engines will contain how many cylinders
    9·2 answers
  • How do energy transformations occur in a hydroelectric plant?
    9·2 answers
  • Which statement describes the process of subduction? Convection currents pull a plate into the mantle. One plate slides beneath
    8·2 answers
  • Work is the quantity of _______________ used to move an object.
    10·1 answer
  • Figure 2 shows the junction of three wires, F, G and H, in a circuit. The current in wire F is 6.0A.
    5·1 answer
  • 5. You are pulling a rubber sneaker along concrete
    8·1 answer
  • Which of the following is not a greenhouse gas?
    12·1 answer
  • If the slump and subsequent flow continue migrating uphill and more material flows downhill, which of the following are a hazard
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!