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3 years ago

NEED BOTH QUESTIONED ANSWERED ASAP.

Physics

1 answer:

Nana76 [90]3 years ago

8 0

Answer:

the answer is the red super giants

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What fraction of all the electrons in a 25 mg water

mihalych1998 [28]

Answer:

$9.11\times 10^{-15}.$

Explanation:

The water droplet is initially neutral, it will obtain a 40 nC of charge when a charge of -40 nC is removed from the water droplet.

The charge on one electron, $\rm e=-1.6\times 10^{-19}\ C.$

Let the N number of electrons have charge -40 nC, such that,

$\rm Ne=-40\ nC\\\Rightarrow N=\dfrac{-40\ nC}{e}=\dfrac{-40\times 10^{-9}\ C}{-1.6\times 10^{-19}\ C}=2.5\times 10^{11}.$

Now, mass of one electron = $\rm 9.11\times 10^{-31}\ kg.$

Therefore, mass of N electrons = $\rm N\times 9.11\times 10^{-31}=2.5\times 10^{11}\times 9.11\times 10^{-31}=2.2775\times 10^{-19}\ kg.$

It is the mass of the of the water droplet that must be removed in order to obtain a charge of 40 nC.

Let it is m times the total mass of the droplet which is $25\ \rm mg = 25\times 10^{-6}\ kg.$

Then,

$\rm m\times (25\times 10^{-3}\ kg) = 2.2775\times 10^{-19}\ kg.\\m=\dfrac{2.2775\times 10^{-19}\ kg}{25\times 10^{-3}\ kg}=9.11\times 10^{-15}.$

It is the required fraction of mass of the droplet.

3 0

3 years ago

The half-life of Iodine-131 is 8.0252 days. If 14.2 grams of I-131 is released in Japan and takes 31.8 days to travel across the

MakcuM [25]

Answer:

Explanation:

Half-life problems are modeled as exponential equations. The half-life formula is $P=P_o\left (\dfrac{1}{2} \right)^{\frac{t}{k}}$ where $P_o$ is the initial amount, $k$ is the length of the half-life, $t$ is the amount of time that has elapsed since the initial measurement was taken, and $P$ is the amount that remains at time $t$ .

$P=14.2\left (\dfrac{1}{2} \right)^{\frac{t}{8.0252}}$

<u>Deriving the half-life formula</u>

If one forgets the half-life formula, one can derive an equivalent equation by recalling the basic an exponential equation, $y=a b^{t}$ , where $t$ is still the amount of time, and $y$ is the amount remaining at time $t$ . The constants a and b can be solved for as follows:

Knowing that amount initially is 14.2g, we let this be time zero:

$y=a b^{t}$

$(14.2)=ab^{(0)}$

$14.2=a *1$

$14.2=a$

So, $a=14.2$ , which represents out initial amount of the substance, and our equation becomes: $y=14.2 b^{t}$

Knowing that the "half-life" is 8.0252 days (note that the unit here is "days", so times for all future uses of this equation must be in "days"), we know that the amount remaining after that time will be one-half of what we started with:

$\left(\frac{1}{2} *14.2 \right)=14.2 b^{(8.0252)}$

$\dfrac{7.1}{14.2}=\dfrac{14.2 b^{8.0252}}{14.2}$

$0.5=b^{8.0252}$

$\sqrt[8.0252]{\frac{1}{2}}=\sqrt[8.0252]{b^{8.0252}}$

$\sqrt[8.0252]{\frac{1}{2}}=b$

Recalling exponent properties, one could find that $\left ( \frac{1}{2} \right )^{\frac{1}{8.0252}}=b$ , which will give the equation identical to the half-life formula. However, recalling this trivia about exponent properties is not necessary to solve this problem. One can just evaluate the radical in a calculator:

$b=0.9172535661...$

Using this decimal approximation has advantages (don't have to remember the half-life formula & don't have to remember as many exponent properties), but one minor disadvantage (need to keep more decimal places to reduce rounding error).

So, our general equation derived from the basic exponential function is:

$y=14.2* (0.9172535661)^t$ or $y=14.2*(0.5)^{\frac{t}{8.0252}}$ where y represents the amount remaining at time t.

<u>Solving for the amount remaining</u>

With the equation set up, substitute the amount of time it takes to cross the Pacific to solve for the amount remaining:

$y=14.2* (0.9172535661)^{(31.8)}$ $y=14.2*(0.5)^{\frac{(31.8)}{8.0252}}$

$y=14.2* 0.0641450581$ $y=14.2*(0.5)^{3.962518068}$

$y=0.9108598257$ $y=14.2* 0.0641450581$

$y=0.9108598257$

Since both the initial amount of Iodine, and the amount of time were given to 3 significant figures, the amount remaining after 31.8days is 0.911g.

8 0

2 years ago

Light-rail passenger trains that provide transportation within and between cities speed up and slow down with a nearly constant

snow_lady [41]

Answer:

26m/s

Explanation:

Assuming that the acceleration is constant, we can start by calculating the train speed when it's free of the congested area:

$a = \frac{\deltav}{\deltat} = \frac{12 - 5}{8} = \frac{7}{8} = 0.875 m/s^2$

Then with the same acceleration we can find out the final speed:

$v = v_0 + at = 12 + 0.875*16 = 26m/s$

3 0

3 years ago

All waves transmit?

PtichkaEL [24]

Answer:

The transmission of energy is one thing that is carried out by all kinds of waves. They transmit energy from one point, known as the source, to another point.

For instance, in electromagnetic waves, energy is transmitted as a result of vibrations between the magnetic field and electric field. In mechanical waves, energy is transmitted when the particles in the medium heat up and vibrate. Energy travels through particles in a medium.

3 0

3 years ago

A horse canters away from its trainer in a straight line, moving 37 m away in 9.1 s. It then turns abruptly and gallops halfway

vesna_86 [32]

Answer:

Average velocity = 1.69 m/s

Average speed = 5.09 m/s

Explanation:

Given that

Horse cover 37 m in 9.1 sec and 18.5 m in 1.8 sec.

As we know that

Average velocity = Displacement / Total time

Average speed = Total distance / Total time

Average velocity:

Average velocity = Displacement / Total time

Total displacement = 37 - 18.5 = 18.5 m

Total time = 9.1 + 1.8 =10.9 s

Average velocity = Displacement / Total time

Average velocity = 18.5 / 10.9

Average velocity = 1.69 m/s

Average speed:

Average speed = Total distance/ Total time

Total distance = 37 + 18.5 = 55.5 m

Total time = 9.1 + 1.8 =10.9 s

Average speed = Total distance/ Total time

Average speed = 55.5 / 10.9

Average speed = 5.09 m/s

3 0

3 years ago