A sample contains 36 g of a radioactive isotope. How much radioactive isotope remains in the sample after 3 half-lives?
A. 12 g
B. 18 g
C. 4.5 g
D. 9 g

la respuesta correcta es la "E"

Answer:

dβ = 70. 77 dβ

Explanation:

The intensity of sound in decibels is

         dβ = 10 log I/I₀

let's look for the intensity of this signal

         I / I₀ = 10 dβ/10

         I / I₀ = 3.981 10⁶

the threshold intensity of sound for humans is I₀ = 1 10⁻¹² W / m²

         I = 3.981 10 ⁶ 1 10⁻¹²

         I = 3,981 10⁻⁶ W / m²

It is indicated that 3 cornets are placed in the circle, for which total intensity is

        I_total - 3 I

        I_total = 3  3,981 10⁻⁶

        I_total = 11,943 10⁻⁶ W / m²

let's reduce to decibels

      dβ = 10 log (11,943 10⁻⁶/1 10⁻¹²)

      dβ = 10  7.077

      dβ = 70. 77 dβ

Answer:

1.2

Explanation:

Answer:

673km

Explanation:

Answer:

The centripetal acceleration for the first radius; 2.0 m = 50 m/s²

The centripetal acceleration for the second radius; 4.0 m = 25 m/s²

The centripetal acceleration for the third radius; 6.0 m = 16.67 m/s²

The centripetal acceleration for the fourth radius; 8.0 m = 12.5 m/s²

The centripetal acceleration for the fifth radius; 10.0 m = 10 m/s²

Explanation:

Given;

mass of the object, m = 1 kg

velocity of the object, v = 10 m/s

different values of the radius, 2.0 m 4.0 m 6.0 m 8.0 m 10.0 m

The centripetal acceleration for the first radius; 2.0 m

[tex]a_c = \frac{v^2}{r} \\\\a_c_1= \frac{(10)^2}{2} \\\\a_c_1= 50 \ m/s^2[/tex]

The centripetal acceleration for the second radius; 4.0 m

[tex]a_c_2= \frac{(10)^2}{4} \\\\a_c_2= 25 \ m/s^2[/tex]

The centripetal acceleration for the third radius; 6.0 m

[tex]a_c_3= \frac{(10)^2}{6} \\\\a_c_3= 16.67 \ m/s^2[/tex]

The centripetal acceleration for the fourth radius; 8.0 m

[tex]a_c_4= \frac{(10)^2}{8} \\\\a_c_4= 12.5 \ m/s^2[/tex]

The centripetal acceleration for the fifth radius; 10.0 m

[tex]a_c_5= \frac{(10)^2}{10} \\\\a_c_5= 10 \ m/s^2[/tex]

Answer:

The magnitude of the friction force is also F.

Explanation:

By the second Newton's law, we know that:

F = m*a

Net force is equal to mass times acceleration.

Here, we know that the box moves with constant speed, thus, the box has no acceleration, then the net force applied to the box is zero.

Also, remember that the friction force is given by:

[tex]F_f = -\mu*W[/tex]

Where mu is the coefficient of friction, and this force opposes to the direction of motion (that coincides with the direction of our forward force, that is why this has a negative sign)

The net force will be equal to the sum of our two horizontal forces (as the weight is already canceled by the normal force)

[tex]F_{total} = F + F_f[/tex]

And this is equal to zero, because we know that the box is non-accelerated.

Then we must have that:

[tex]F_f = -F[/tex]

Then we can conclude that the magnitude of the friction force is F.

Answer:

a)    F = 35.7 N, b)   W = 846.7 J, c)   W = - 846.9 J, d) W=0

Explanation:

a) For this exercise let's use Newton's second law, let's set a reference frame with the x-axis horizontally

let's break down the pushing force.

        cos (-23,7) = Fₓ / F

        sin (-237) = F_y / F

        Fₓ = F cos 23.7 = F 0.916

        F_y = F sin (-23.7) = - F 0.402

Y axis  

       N- W - F_y = 0

       N = W + F 0.402

X axis

       Fₓ - fr = 0

       F 0.916 = fr

       F = fr / 0.916

       F = 32.7 / 0.916

       F = 35.7 N

It is asked to calculate several jobs

b) the work of the pushing force

       W = fx x

       W = 35.7 cos 23.7 25.9

       W = 846.7 J

c) friction force work

        W = F x cos tea

friction force opposes movement

        W = - fr x

         W = - 32.7 25.9

         W = - 846.9 J

d) The work of the force would gravitate, as the displacement and the force of gravity are at 90º, the work is zero

          W = 0

Answer:

plz mark brainliest again lol :)

Explanation:

When you drop a ball from a greater height, it has more kinetic energy just before it hits the floor and stores more energy during the bounce—it dents farther as it comes to a stop.

Answer:

When you drop a ball from a greater height, there is more potential energy. When you release the ball, the potential energy turns into kinetic energy. When the ball bounces off the ground, the ball go upward and then it has more potential energy. Then when it goes down it has more kinetic energy. The ball keeps doing this until there is not enough potential energy left.

Explanation:

Answer:

Fission is used in nuclear power reactors since it can be controlled, while fusion is not utilized to produce power since the reaction is not easily controlled and is expensive to create the needed conditions for a fusion reaction.

Explanation:

Answer:

Hello There!!

Explanation:

I think it is A. Fusion requires very high pressure and temperature. Sorry if I am wrong.

hope this helps,have a great day!!

~Pinky~

Answer:

c

Explanation:

Superconductors perform best at very cold temperatures because resistivity of this kind of materials decays drastically with temperature. Chromium is most likely to be the best conductor of electricity because it belongs to the Transition Metal group of the periodic table

Answer:

The ratio of the electrostatic force to the gravitational force between the electrons is 4.181 x 10⁴²

Explanation:

Given;

charge of electron, Q = 1.602 x 10⁻¹⁹ C

mass of an electron, m = 9.1 x 10⁻³¹ kg

distance between the two electrons, r = 6.64 x 10⁻¹¹ m

The electrostatic force between the electrons is calculated using Coulomb's law;

[tex]F_e = \frac{kQ^2}{r^2} \\\\F_e = \frac{(9\times 10^9)(1.602 \times 10^{-19})^2}{(6.64 \times 10^{-11})^2} \\\\F_e = 5.239 \times 10^{-8} \ N[/tex]

The gravitaional force between the electrons is calculated as;

[tex]F_g = \frac{Gm^2}{r^2} \\\\F_g = \frac{(6.67\times 10^{-11})(9.1 \times 10^{-31})^2}{(6.64\times 10^{-11})^2} \\\\F_g = 1.253 \times 10^{-50} \ N[/tex]

The ratio of the electrostatic force to the gravitational force between the electrons;

[tex]\frac{F_e}{F_g} = \frac{5.239\times 10^{-8}}{1.253 \times 10^{-50}} = 4.181 \times 10^{42}[/tex]

Answer:

The option (B) is correct.

Explanation:

The magnetic force between the two current carrying wires is given by

[tex]F =\frac{\mu o}{4\pi}\times \frac{2 I I'}{r}[/tex]

where,  I and I' be the currents in the wires and r is the distance between the two wires.

Here, we observe that the force between the wires is inversely proportional to the distance between them.

So, when the distance is doubled , let the new force is F'.

[tex]\frac{F'}{F}=\frac{r}{r'}\\\\\frac{F'}{F}=\frac{d}{2d}\\\\F'=\frac{F}{2}[/tex]

So, option (B) is correct.

Answer:

Explanation:

Use the one-dimensional equation

Δx = [tex]v_0t+\frac{1}{2}at^2[/tex] where delta x is the displacement of the object, v0 is the velocity of the object, a is the pull of gravity, and t is the time in seconds. That's our unknown.

Δx = -2 (negative because where it ends up is lower than the point at which it started),

[tex]v_0=5[/tex], and

a = -9.8

Filling in:

[tex]-2=5t+\frac{1}{2}(-9.8) t^2[/tex] and simplified a bit:

[tex]-2=5t-4.9 t^2[/tex]

this should look hauntingly familiar (a quadratic, which is parabolic motion...very important in physics!!). We begin by getting everything on one side of the equals sign and solving for t by factoring:

[tex]-4.9 t^2+5t+2=0[/tex] (the 0 is also indicative of the object landing on the ground! Isn't this a beautiful thing, how it all just works so perfectly together?)

When you factor this however your math/physics teacher has you factoring you will get that

t = 1.3 sec and t = -.31 sec

Since we all know that time can NEVER be negative, it takes the ball 1.3 sec to hit the ground from a height of 2 m if it is rolling off the shelf at 5 m/s.

Answer:

- the effective lift area for the aircraft is 8.30 m²

- the required engine thrust is 1275 N

- required power is 79.7 kW

Explanation:

Given the data in the question;

Speed V = 225 km/hr = 62.5 m/s

The lift coefficient CL = 0.45

drag coefficient CD = 0.065

mass = 900 kg

g = 9.81 m/s²

a)  the effective lift area for the aircraft

we know that for a steady level flight, weight = lift and thrust = drag

Using the equation for the lift force

F[tex]_L[/tex] = C[tex]_L[/tex][tex]\frac{1}{2}[/tex]ρV²A = W

we substitute

0.45 × [tex]\frac{1}{2}[/tex] × 1.21 × ( 62.5 )² × A = ( 900 × 9.81 )

1081.05 × A = 8829

A = 8829 / 1081.05

A = 8.30 m²

Therefore, the effective lift area for the aircraft is 8.30 m²

b) the required engine thrust and power to maintain level flight.

we use the expression for drag force

F[tex]_D[/tex] = T = C[tex]_D[/tex][tex]\frac{1}{2}[/tex]ρV²A

we substitute

= 0.065 × [tex]\frac{1}{2}[/tex] × 1.21 × ( 62.5 )² × 8.30

T = 1275 N

Since drag and thrust force are the same,

Therefore, the required engine thrust is 1275 N

Power required;

P = TV

p = 1275 × 62.5

p = 79687.5 W

p = ( 79687.5 / 1000 )kW

p = 79.7 kW

Therefore, required power is 79.7 kW

Answer:

v = 0.5 m/s.

Explanation:

Total distance, d = 20 m + 20 m = 40 m

Total time taken, t = 30 s + 50 s = 80 s

The average speed of an object is the total distance divided by time taken. So,

[tex]v=\dfrac{40}{80}\\\\=0.5\ m/s[/tex]

So, the average speed of the object is 0.5 m/s.

Answer:

Explanation:

The energy of a photon is given by the Planck relation

          E = h f

the speed of light is related to wavelength and frequency

          c = λ f

           f- c /λ

we substitute

          E = h c /λ

let's calculate

          E = 6.63 10-34 3 10⁸ / 550 10-9

          E = 3.616 10-19 J

let's reduce to eV

          E = 3.616 10-19 J (1 eV / 1.6 10-19)

          E = 2.26 eV

Answer:

Following are the solution to the given question:

Explanation:

Its strength from both charges is equivalent or identical. The power is equal. And it is passed down

[tex]F=\frac{kq_1q_2}{r^2}[/tex]

Therefore, the extent doesn't rely on the fact that charges are the same or different. Newton's third law complies with Electrostatic Charges due to a couple of charges. They are similar in magnitude, and they're in the other way.

[tex]|F_{12}| = |F_{21}|[/tex]

Answer:

translate it to English plss

Answer:

Please find the complete question in the attached file.

Explanation:

This graph as seen in the question must not be trusted. The reason for this is the plotted line of genesis desnt.

F=Ma

When F is in the axis (x,y) and mass of the system of the arc must be plotted  F = 0 if a = 0 is considered as the perfectly friction-less ground.

This might be the case, as noted correctly, with such a surface tension opposite our twisting motion, in there is a coercing vertex even when the velocity of the body is zero, that is an example of friction force where the beginning pressure is working against frictional without moving or speeding up the body.

Concerning whatever the students got right, the complete experiment I knew is only evaluated correctly, but some of the suggestions clean the surface before exp, place the oil surface film and doing the experiment on an emptied ship; minimize that friction component.

The convection zone is the area of the sun does gas rise as it heats up, then fall back down as it cools.

This part of the Sun is found below the photosphere and helps isn the area where the form of heat transfer known as Convection takes place.

This occurs when heated gases rise up and then falls back when cooled as a result if hot gases being less dense.

Read more about Convection zone here https://brainly.com/question/22542880

Answer: See explanation

Explanation:

Climate change, is also referred to as global warming, and it simply means the rise in Earth's average surface temperature.

Effects of climate change include rising sea levels, heat waves, drought, storms, etc.

Extreme heat events is dangerous to the health of both animals and humans. For human beings, it can bring about increase in heat- related illness, weakness, heat stroke and excessive water consumption.

For animals, it can lead to struggling of the animals in losing their excess body heat by evaporation. Other effects include panting, loss of appetite, increased drinking, difficulty breathing, anxious behaviour, and weakness.

Answer:

At the earth's surface  g = G M / R^2        where G is the gravitational constant

at H       g1 = G M / (R + H)^2         using Gauss' theorem for enclosed mass

g1 = G M / (R^2 + 2 R H)    ignoring H^2 as it is small compared to R^2

g / g1 = (R^2 + 2 R H) / R^2 = 1 + 2 R H

g = g1 + 2 R H g1

g1 - g = - 2 R H     or H = (g1 - g) / 2 R

Answer:

Put the 2 light bulbs in series.

Explanation:

The resistance will be the greatest if you hook up the light bulb in series, and since resistance and current are inversely proportional, the current will be the least as well.

Answer:

The answer is "0.2711  m/s".

Explanation:

Potential energy = Kinetic energy + Potential energy

[tex]m_1 gh =\frac{1}{2} m_1v^2 +\frac{1}{2} m_2v^2 + \frac{1}{2} I\omega^2 + m_1gh\\\\[/tex]

[tex](m_1- m_2)gh =\frac{1}{2} m_1v^2 +\frac{1}{2} m_2v^2 +\frac{1}{2} I\omega^2\\\\2(m_1 - m_2)gh = m_1v^2 + m_1v^2 + I\omega^2\\\\solid \ disk (I) = \frac{1}{2} \ \ M r^2 \\\\[/tex]

When there is no slipping, \omega  =\frac{ v]{r}\\\\  

[tex]2(m_1 - m_2)gh = m_1v^2 + m_2v^2 + (\frac{1}{2} Mr^2) (\frac{v}{r})^2\\\\2(m_1 -m_2)gh = m_1v^2 + m_2v^2 + \frac{1}{2} Mv^2\\\\4(m_1 -m_2)gh = 2m_1v^2 + 2m_2v^2 + Mv^2\\\\4(m_1 - m_2)gh = (2m_1 + 2m_2 + M) v^2\\\\[/tex]

[tex]v^2 = \frac{4(m_1 - m_2)gh}{(2m_1 + 2m_2 + M)}v[/tex]

[tex]v^2 = \frac{4 (0.25 \ kg - 0.20 \ kg) (9.8 \frac{m}{s^2}) (0.21 m)}{ (2 \times 0.25 kg + 2 \times 0.20 kg + 0.50 kg)}[/tex]

[tex]=\frac{0.1029}{1.4} \ \ \frac{m^2}{s^2}\\\\=0.0735\ \ \frac{m^2}{s^2}\\\\= 0.2711 \ \frac{m}{s}[/tex]

Answer:

because thermometric liquid readily expands on heating or contracts on cooling even for a small difference in the temperature of the body.