(3)science who ever gets this right will get a brainlest

A freshly prepared sample of radioactive isotope has an activity of 10 mCi. After 4 hours, its activity is 8 mCi. Find: (a) the

Maurinko [17]

Answer:

(a). The decay constant is $1.55\times10^{-5}\ s^{-1}$

The half life is 11.3 hr.

(b). The value of N₀ is $2.38\times10^{11}\ nuclei$

(c). The sample's activity is 1.87 mCi.

Explanation:

Given that,

Activity $R_{0}=10\ mCi$

Time $t_{1}=4\ hours$

Activity R= 8 mCi

(a). We need to calculate the decay constant

Using formula of activity

$R=R_{0}e^{-\lambda t}$

$\lambda=\dfrac{1}{t}ln(\dfrac{R_{0}}{R})$

Put the value into the formula

$\lambda=\dfrac{1}{4\times3600}ln(\dfrac{10}{8})$

$\lambda=0.0000154\ s^{-1}$

$\lambda=1.55\times10^{-5}\ s^{-1}$

We need to calculate the half life

Using formula of half life

$T_{\dfrac{1}{2}}=\dfrac{ln(2)}{\lambda}$

Put the value into the formula

$T_{\dfrac{1}{2}}=\dfrac{ln(2)}{1.55\times10^{-5}}$

$T_{\dfrac{1}{2}}=44.719\times10^{3}\ s$

$T_{\dfrac{1}{2}}=11.3\ hr$

(b). We need to calculate the value of N₀

Using formula of $N_{0}$

$N_{0}=\dfrac{3.70\times10^{6}}{\lambda}$

Put the value into the formula

$N_{0}=\dfrac{3.70\times10^{6}}{1.55\times10^{-5}}$

$N_{0}=2.38\times10^{11}\ nuclei$

(c). We need to calculate the sample's activity

Using formula of activity

$R=R_{0}e^{-\lambda\times t}$

Put the value intyo the formula

$R=10e^{-(1.55\times10^{-5}\times30\times3600)}$

$R=1.87\ mCi$

Hence, (a). The decay constant is $1.55\times10^{-5}\ s^{-1}$

The half life is 11.3 hr.

(b). The value of N₀ is $2.38\times10^{11}\ nuclei$

(c). The sample's activity is 1.87 mCi.

4 0

3 years ago

The intensity level is 65 db at a distance 5.00 m from a barking dog. What would be a reasonable estimate for the intensity leve

BARSIC [14]

Answer:

68 db

Explanation:

Since now instead of one two dogs are barking simultaneously close to each other, therefore we take n =2.

Ignoring interference effects, the barking of two dogs result in a higher level of intensity which is given by,

β(db)=10×㏒(2)

=3 db

So, a reasonable estimate for the raised Intensity Level is: 65db+3db = 68db

7 0

3 years ago

__________________________ are made of rock or metal, which often collide with Earth

konstantin123 [22]

Answer:

Planets are bodies of rock or gas that are named after ancient gods.

Asteroids and Meteoroids are made of rock or metal, which often collide with Earth.

The terrestrial planets are more like the Earth.

The Juno spacecraft is exploring the planet Jupiter.

Explanation:

The planets and other stars in our solar system were similarly baptized. The planets were named after ancient gods. Other stars were baptized with names chosen by scientists or according to their peculiarity. Most of the planets were baptized by ancient Chinese astronomers, and later, by Babylonians. But over time different civilizations changed the names of the planets.

An asteroid is a smaller body in the solar system, usually on the order of just a few hundred kilometers. Meteoroids, in turn, are fragments of rocks that form from comets and asteroids. The luminous effect is produced when fragments of celestial bodies ignite in contact with the Earth's atmosphere due to friction. Both asteroids and meteoroids are made of rock or metal, which often collide with Earth.

The terrestrial planets are the most similar to the earth. These planets are those formed mainly by rocks and metals, have a solid surface without the incidence of rings, as is the case with Mercury, Venus and Mars.

The Juno spacecraft is exploring the planet Jupiter. This probe has already given us several unprecedented discoveries about the largest gas giant in the Solar System, in addition to sending us sensational images showing the complex and beautiful atmosphere of the planet.

6 0

3 years ago

Read 2 more answers

In which material does the light wave have the larger wavelength?

pochemuha

Answer: in the smaller/ thinner pieces.

8 0

2 years ago

4. An electric iron has a

Licemer1 [7]

Answer:

4.

a) W = 750 J

b) W = 2250 J

c) t = 2 sec

5. Answered in explanation

Explanation:

4.

The formula of power is given as:

P = W/t

where,

P = Power

W = Work Done

t = Time Taken

a)

Here,

P = 750 W

t = 1 sec

W = ?

Therefore,

750 W = W/1 sec

W = 750 J

b)

Here,

P = 750 W

t = 3 sec

W = ?

Therefore,

750 W = W/3 sec

W = (750 W)(3 sec)

W = 2250 J

c)

Here,

P = 750 W

t = ?

W = 1500 J

Therefore,

750 W = 1500 J/t

t = 1500 J/750 W

t = 2 sec

5.

According to Kinetic Particle Theory, the molecules are tightly packed with each other, by strong inter-molecular forces and they can only vibrate at their position. While, molecules or particles in liquids have lesser attractive forces among them. They can move in layers and can take the shape of any container. This is the reason why solid has a definite shape and liquid has none.

6 0

2 years ago