Can lunar eclipses only be found in the fall?

Janet ran 30 meters in 4 seconds,what is her speed.

lubasha [3.4K]

Answer:

7.5 meters per second

Explanation:

30 / 4 = 7.5

7.5 * 1 = 7.5

7.5 * 2 = 15

7.5 * 3 = 22.5

7.5 * 4 = 30

8 0

3 years ago

Read 2 more answers

An amateur astronomer looks at the moon through a telescope with a 15-cm-diameter objective. What is the minimum separation betw

Lana71 [14]

Answer:

y = 128.0 km

Explanation:

The minimum separation of two objects is determined by Rayleygh's diffraction criterion, which establishes that two bodies are solved if the first minino of diffraction of one coincides with the central maximum of the second, with this criterion the diffraction equation remains

the diffraction equation for the first minimum is

a sin θ = λ

In the case of circular openings, the equation must be solved in polar coordinates, leaving the expression, we use the approximation that the sine of tea is very small.

θ = 1.22 λ / d

d = 15 cm

to find the distance we can use trigonometry

tan θ = y / L

tan θ = sin θ / cos θ = θ

substituting

y / L = λ / d

y = L λ /d

let's calculate

y = 384 10⁸ 500 10⁻⁹ / 0.15

y = 1.28 10⁵ m

Let's reduce to km

y = 1.28 10⁵ m (1km / 10³ m)

y = 128.0 km

the correct answer is 120 km away

5 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 $t$ .

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

Deriving the half-life formula

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.

Solving for the amount remaining

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

1 year ago

Classify each change (which can be manipulated within the green box) according to its effect on the wavelength.

Nataly_w [17]

Answer:

Explanation:

The classification will be made into 3 categories, which are

Ones that shortens wavelengths

Ones that lengthens wavelengths

Ones that has no effect on wavelengths

Shortens wavelengths -> Increase frequency

Lengthens wavelengths -> Decrease frequency

No effect -> Increase amplitude, decrease amplitude, increase damping, decrease damping.

7 0

2 years ago

When an ocean plate converges with another plate, what is created on the seafloor at the line of convergence?

drek231 [11]

When two oceanic plates meet, the process of subduction occurs. During this, the denser plate slips underneath the lighter one, creating a subduction zone. In these subduction zones, a trench is formed.
Trenches are deep crevices on the ocean floor and are home to many different marine species.

5 0

2 years ago