A radioactive sample starts with 800,000 undecayed nuclei. After 12 hours, 700,000 of the nuclei have decayed. What is the half-life of the sample?

A. 3 hours

B. 12 hours

C. 6 hours

D. 4 hours

Answers

Answer 1

Answer:

100,000 / 800,000 = 1 / 8    amount of sample after 12 hours

(1/2)^n = 1 / 8      after n half-lives 1/8 of sample will be left

n = 3

(D) is the correct answer - 1/2 half-life = 4 hours


Related Questions

Which is an example of current electricity

Answers

Answer:

A or B you choose

Explanation:

This is called current electricity or an electric current. A lightning bolt is one example of an electric current, although it does not last very long. Electric currents are also involved in powering all the electrical appliances that you use, from washing machines to flashlights and from telephones to MP3 players.

what is an electrical current, amp, ampere Current is the flow of electrons. When a circuit is closed then a current of electrons can flow and when a circuit is open then no current can flow. We can measure the flow of electrons just like you can measure the flow of water through a pipe.

High energetic winds turning generator , causing electrons to flow into power lines is an example of current electricity. Remaining all are examples of static electricity .

What is current electricity ?

The movement of electrons from one area of the circuit to another is referred to as current electricity. Free electrons flow between two points when two bodies with different potentials are connected by a wire, until both objects reach the same potential, at which point the current stops.

Current flows until a potential difference exists throughout the conductor. The following techniques can be used to produce current electricity:

1. Through the passage of a metal wire through a magnetic field (Both alternating current and direct current can be generated by the following method)

2.Utilizing a battery and chemical reactions (Direct current can be generated through this method)

Here, the wind's kinetic energy provide the mechanical energy for the generator to to produce power lines. Hence option A is correct. All others are static electricity for short time only.

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The headlights of a typical car are powered by a 12 v battery. What is the resistance of the headlights if they draw 3.0 A if a current when turned on

Answers

Answer:

4 ohms

Explanation:

V = I R

12 = 3 R

R = 4 ohms

If the distance between two objects is tripled, what happens
to the gravitational force between them?
A. It decreases to 1/3 its original magnitude.
B. It increases to 9 times its original magnitude.
C. It increases to 3 times its original magnitude.
D. It decreases to 1/9 its original magnitude.
.

Answers

Answer:

D)it decreases to 1/9 its original magnitude

6. Aste owing questions 1. Answer question i and ii based on the information given below. In biology laboratory, Tashi observed a cell under a microscope. While on the cell, his attention was drawn to a tiny star like close to a large dense spherical body at the centre. He also observer many rod shaped structures scattered inside the cell. (i) Identify the cell organelles observed by Tashi. body a (ii) Is it a plant cell or an animal cell? 3. Study the diagram of a cell in Figure 1.8 and answer the following questions. i. In which group of organisms would you find this cell? Give reasons to support your answer. ii. Name the parts labelled A, B, C, and D. B TO D​

Answers

The cell is an animal cell and the rod-shaped structures in the cell are mitochondria.

What are cell organelles?

Cell organelles are membrane-bound structures found within the cell of eukaryotes which carry out specific functions in the cell.

Some cell organelles include:

mitochondria ribosomes Golgi bodies endoplasmoc reticulum

The rod-shaped structures in the cell are mitochondria.

Asters are star-shaped structures found within the cell which are found close to the nucleus d

at the early mitosis in an animal cell.

Asters do not form during mitosis in plants.

Therefore, the cell is an animal cell and the rod-shaped structures in the cell are mitochondria.

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what is the mass of 2.4 moles of water ​

Answers

Answer:

43.2

2.4×18

18 is the molar mass of water

multiply the no of moles with the molar mass to find the mass of the substance

Answer:

43.25 grams

Explanation:

one mole of H2O is 18.02 grams

18.02*2.4=43.248 grams

Hello people ~
On charging by conduction, mass of a
body may

(a) increase

(b) decreases

(c) increase or decrease

(d) None of these

Answers

increase or decrease

body gains mass when gets negative charge/electronsbody losses mass when gets positive charge/losses electrons

Thus the mass may increase and  decrease due to conduction || varies

What is it called when something with kinetic energy(something moving) hits something that is still / has potential energy

Answers

Answer:

It is called Motion Energy

Explanation:

(b) When the taps are opened, water flows in the pipe for some time. The diagram shows the final water level in container (i) Complete the diagram to show the final water level in container B.
(ii) Explain why the water starts to flow and then stops.​

Answers

ii) The pressure difference in the two containers starts the flow of the water from container A to B until the pressure becomes equal in both the containers. Pressure causes force on water, because pressure = force/area

Please help

how long have people used coal as a source of fuel
A. 200 years
B. 1000 years
C. 3000 years
D. 5000 years

Answers

Answer:

c. 3,000

Explanation:

I am guessing 3000 years

A hiker climbs a hill 300m high. If she has a mass of 51kg, calculate the work she does in lifting her body to the top of the hill​

Answers

Answer:

153000J

Explanation:

[tex]work \: done = \: force \times distance \\ force = mass \times acceleration \: due \: to \: gravity \\ = 51 \times 10 \\ = 510newton \\ work \: done = 510 \times 300 \\ = 153000joules[/tex]

The voltage in american household is 120 v. however, because we use a/c power, the voltage is oscillating between two maximums. what is the maximum or peak voltage required to produce an average voltage of 120 v?.

Answers

Answer:

188 v

Explanation:

The average of a sine wave is .637 times the peak value

.637 x = 120

x = 120 / .637 = 188 v

The voltage in an American household is 120 v. however because we use a/c power, the voltage is oscillating between two maximums, then the maximum or peak voltage required to produce an average voltage of 120 Volts would be 76.44 Volts.

What is power?

The rate of doing work is known as power. The Si unit of power is the watt.

Power = work / time

The mathematical expression for the power is as follows

P = VI

As given in the problem, the voltage in American household is 120 v. however, because we use a/c power, the voltage is oscillating between two maximums.

The average voltage (VAV) of a sinusoidal waveform is determined by multiplying the peak voltage value by the constant 0.637, which is two divided by pi (π).

The maximum voltage = 120 × 0.637

                                      =  76.44 Volts

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The diagram shows the water levels inside the containers.
A)91 cm
B) 34 cm ( the water levels)
•) The density of water is 1000 kg/m²
ii) Calculate the pressure that the water causes at the base of container A.​

Answers

Answer:

8927.1 Pa

Explanation:

pressure = height x density of liquid x g

               = (91/100) x 1000 x 9.81

               = 8927.1 Pa

If we say that a galaxy has a lookback time of 1 billion years, we mean that _________.

Answers

If we say that a galaxy has a lookback time of 1 billion years, we mean that its light traveled through space for 1 billion years to reach us.

have a great day!

how are the four chambers in the heart connected by it

Answers

Answer:

I think it is  atrioventricular valves

Explanation:

hope this helps

Below, you will see a nuclear fission reaction: NUCLEAR FISSION A neutron slams into a Uranium-235 atom beginning the fission process. The products of this reaction are: Barium-141; Krypton-92; and 3 neutrons. + + + + + Please write the equation in the blanks below:​

Answers

The nuclear fission reaction of Uranium-235 atom produces Barium-141, Krypton-92 and 3 neutrons.

What is nuclear fission?

Nuclear fission is a nuclear reaction in which the atomic nucleus of a heavier element disintegrates or splits to produce two or more atoms of elements with smaller nuclei.

The nuclear fission reaction in which a neutron is used to bombard the nucleus of Uranium-235 atom to produce Barium-141, Krypton-92 and 3 neutrons is given below

[tex]_{235}U + \: _{1}n^{o} \rightarrow \: _{141}Ba+ \: _{92}Kr + 3 \: _{1}n^{o} [/tex]

Therefore, the nuclear fission reaction of Uranium-235 atom produces Barium-141, Krypton-92 and 3 neutrons.

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Which magnet would be best for lifting heavy metal, moving it,and letting go of it

Answers

The electromagnet. It’s controlled by an electric coil

A transformer has 1,000 turns of wire in the primary coil and 50 turns in the secondary coil. If the input voltage is 2,400 V, what is the output voltage? - this is for my physical science class

Answers

the output voltage of the transformer that has 1,000 turns of wire in the primary coil and 50 turns in the secondary coil is 120 V

What is a transformer?

A transformer is an electrical device that transfer electric energy from one circuit to another.

To calculate the output voltage of the transformer, we use the formula below.

Formula:

V/V' = N/N'........... Equation 1

Where:

V = Primary/input VoltageV' = Secondary/output voltageN = Primary turnsN' = Secondary turns

Make V' the subject of the equation

V' = VN'/N........... Equation 2

From the question,

Given:

V = 2400 VN' = 50 turnsN = 1000 turns.

Substitute these values into equation 2

V' = (2400×50)/1000V' = 120 V

Hence, the output voltage of the transformer that has 1,000 turns of wire in the primary coil and 50 turns in the secondary coil is 120 V.

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5. The amount of energy provided by a battery in a circuit is
the amount of energy consumed in the circuit.

A. Equal to
B. Less than
C. Greater than
D. Not related to

Answers

Electric power is the rate, per unit time, at which electrical energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second. So the answer is C
5. The amount of energy provided by a battery in a circuit is
the amount of energy consumed in the circuit.

C. Greater than

The photograph shows a kettle made of the element copper. Which statement describes a chemical property of copper?

A. Copper forms a patina when it interacts with air.

B. Copper is a solid at room temperature.

C. Copper is a good conductor of electric current.

D. Copper can be re-shaped when hit with a hammer.

Answers

A copper forms a patina when it interacts with air
Answer A
Explanation
B describes its matter (composition)
C describes its ability to conduct
D describes is mailability

A describes a chemical reaction with the air

The density of water is 1.0 gram per milliliter at 4 degrees Celsius.
Shelby drops a spoonful of sugar into water at this temperature and it
sinks to the bottom of the container. Compare the densities of the sugar
and water and explain how this affects the position of the sugar in the
liquid water.

Answers

Sugar molecules present at the bottom of solution due to more mass.

Which is more denser water or sugar?

Table sugar is more dense than water due to the presence of more mass of sugar molecule as compared to water. We know that denser objects has more mass so that's why sugar molecules present at the bottom of solution due to more mass.

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Which two characteristics might a model have if it is a three-dimensional model of magnetic force made by using a magnet and magnetic field lines? A. Some field lines have arrows that point in different directions. B. Arrows on the field lines point from the magnet's north pole to its south pole. C. The field lines are closest together in and near the magnet D. The field lines cross paths as they go from one pole of the magnet to the other.​

Answers

Answer:

 B C     I suppose , though A is correct too

Explanation:

The arrows on the magnetic field lines point from the magnet's north pole to its south pole. The field lines are closest together in and near the magnet. Thus, the correct options are B and C.

What is Magnetic force?

Magnetic force is the force of the electrically charged particles which are in motion, such as attraction, or repulsion results from their activity. It is the fundamental force behind the phenomena like how electric motors operate and magnets are drawn to metals.

Usually, when we draw magnetic field lines, we start to draw outwardly from the North pole to the South Pole. This same direction is prevalent on the Earth due to the fact that the Earth functions as a giant magnet. Thus, the model describes that the magnetic field lines will spread out of the north end of the magnet to the south end. The magnetic field lines are closest in and near the magnet.

Therefore, the correct options are B and C.

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You want to determine whether the mass of an object attached to a parachute affects the time it takes to fall to the ground. In this investigation, would "the material the parachute is made out of" be a suitable control variable? no or yes​

Answers

The material the parachute is made out of" will not be a suitable control variable as it is needed in the research.

What is a control variable?

It should be noted that a control variable simply means any variable that is held constant in a research.

In this case, the material the parachute is made out of" will not be a suitable control variable as it is needed in the research.

Therefore, it's false.

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Determino la masa en gramos y kilogramos de 1500 cm3 de alcohol etílico, cuya densidad es aproximadamente 790.0 Kg/m3. Tomar en cuenta que: Densidad (ρ) = masa (m)/volumen(v).

Answers

Para calcular el contenido en gramos de una bebida alcohólica basta con multiplicar los grados de la misma por la densidad del alcohol (0,8). El contenido de alcohol de una bebida depende de la concentración de alcohol y del volumen contenido.

The mass in grams and in kilograms of ethyl alcohol respectively is: a) 1185.0 g and b) 1185 kg

What is density?

Density is an intensive property of matter. It represents the relationship between the mass and the volume of a body or substance. Its units are in the International System kg/m3, kg/L, g/ml, g/cm3, among others.

The density formula is:

Density = m/V

The mass is obtained by clearing this equation

m=Density *Volume

data

m= ?

V= 1500 cm3 * 1 * 10⁻⁶ m³ / 1 cm³ = 0.0015 m³ = 1.5 * 10⁻³ m₃

Density= 790.0 kg/m3

m = 790.0 kg/m³ * 1.5 * 10⁻³m³ = 1.185 Kgm = 1.185 kg * 1000 g/ 1 kg = 1185,0 gm=  1185,0 g

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If you see fog, what can you know about the temperature and dewpoint near the ground? (Just a simple-ish, short answer please.)

Answers

Answer:The difference between air temperature and dew point is less than 4.5 degrees Fahrenheit when fog can form.

Explanation:This can occur because of added moisture or falling air temperatures. The difference between air temperature and dew point is less than 4.5 degrees Fahrenheit when fog forms.

What fraction of chlorine-36 remains UN-decayed after 800,000 years?

Answers

Three quarters remain un-decayed

Which of the following is NOT a chemical change/reaction?

Question 3 options:

2 liquids are combined, and a solid precipitate is formed


phase/state change (solid, liquid, gas)


production of gas bubbles


rusting metal

Answers

Answer:

rusting metal I think hehe

The potential energy of a swing is 200 j at its highest point and 50j as its lowest point energy is conserved ,what is the kinetic energy of the swing at its lowest point

Answers

Answer:

150J

Explanation:

yee thats it hope it helps

If the gravitational force on an object is directly proportional to its mass, why don’t objects with large masses fall with greater acceleration than small ones?.

Answers

Heavier things have a greater gravitational force AND heavier things have a lower acceleration. It turns out that these two effects exactly cancel to make falling objects have the same acceleration regardless of mass.

Ers), and

1. A paintball with a mass of 0. 15 kg is fired from a paintball gun that has a mass of 5. 5 kg. The paintball leaves the

gun with a velocity of 45 m/s [N] having accelerated for only 0. 10 s. Calculate the acceleration and the final

velocity of the paintball gun.


Please help

Answers

Answer:

-13.5 m/s^2

-1.35m/s

Explanation

First, find the momentum of the paintball by using the formula [tex]p=mv[/tex].

[tex]p=0.15*45[/tex]

[tex]p = 6.75[/tex]

The next step would be to find the change of momentum of the gun. Since the gun was at rest it had a momentum of 0. Momentum acts in different directions equally, therefore we can set up the equation for the acceleration:

FΔt=Δp

Where F is force, Δt is the change of time and Δp is the change of momentum.

Since we solve for acceleration, we can convert F to ma to get:

maΔt=Δp

Substitute values:

5a*(0.1-0)=-6.75

5a=-67.5

a=-13.5

Our a is -13.5m/s^2, it's negative since the direction it's acting on is opposite of the paintball.

Now we can find velocity (and double-check our work!).

The first way to solve for velocity is:

[tex]V=Vi+at[/tex]

Where V is final velocity, Vi is initial, a is acceleration and t is time.

substitute values:

[tex]V=0-13.5*0.1\\V=-1.35m/s[/tex]

If we are correct, using the formula p=mv, we should get the same result (remember, our momentum is negative).

[tex]p=mv\\-6.75=5v\\-1.35m/s=v[/tex]

Hope this helps!

Find the ( mass m ) when system is equilibrium help me pleasee this choice is
1. 4 kg
2. 6.25 kg
3. 10 kg
4. 12.5 kg
5. 25 kg
please show solution ​

Answers

Answer:

5. 25 [kg].

Explanation:

1) the final ratio is:

m_20kg *g=m*g/cos37°; ⇒ m= m_20kg / cos37°;

2) answer is:

m=20/0.8=25 [kg].

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