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Simora [160]
3 years ago
9

A motorboat travels 9 miles downstream (with the current) in 30 minutes. The return trip upstream (against the current) takes 90

minutes.
Which system of equations can be used to find x, the speed of the boat in miles per hour, and y, the speed of the current in miles per hour? Recall the formula d = rt.


9 = 0.5(x _ y)
9 = 1.5(x + y)

9 = 1.5(x _ y)
9 = 0.5(x + y)

0.5 = 9(x _ y)
1.5 = 9(x + y)

1.5 = 9(x _ y)
0.5 = 9(x + y)
Physics
2 answers:
Contact [7]3 years ago
7 0

9 = 1.5(x – y)

9 = 0.5(x + y)

Answer: B

Yanka [14]3 years ago
5 0
When moving with the current, the speeds of the boat and current will add up. The first situation can then be represented by:
9 = 0.5(x + y)
While opposing the current, the speeds will be subtracted. Forming:
9 = 1.5(x - y)
The second option contains this equation system, so it is correct.
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vodka [1.7K]

Answer:

u = 449 m/s

Explanation:

Given,

Mass of the bullet, m = 26 g

Mass of the wooden block,M = 4.7 Kg

height of the block,h = 0.31 m

initial speed of the block, u = ?

Using conservation of energy

(M+ m)gh = \dfrac{1}{2}(M+m)v^2

gh = \dfrac{1}{2}v^2

v=\sqrt{2gh}

v=\sqrt{2\times 9.81\times 0.31}

v = 2.47 m/s

Now, using conservation of momentum to calculate the speed of the bullet.

m u + M u' = (M+m)v

m u  = (M+m)v

0.026 x u  = (4.7+0.026) x 2.47

u = 449 m/s

Hence, the speed of the bullet is equal to 449 m/s.

5 0
3 years ago
The properties of each state of a substance are due largely to the degree (amount) of intermolecular bonding. True False
marysya [2.9K]

Answer:

true

Explanation:

6 0
3 years ago
Simplified. The absorption spectra of ions have been used to identify the presence of the elements in the atmospheres of the sun
Nookie1986 [14]

Answer:

The answer is "3.83 \times 10^9 \ m"

Explanation:

Z=2, so the equation is E= \frac{-4B}{n^2}

Calculate the value for E when:  

n=2 and n=9

The energy is the difference in transformation, name the energy delta E Deduct these two energies  

In this transition, the wavelength of the photon emitted is:

\Delta E=2.18 \times  10^{-18} ( \frac{1}{4}- \frac{1}{81})

\lambda = \frac{h c}{\Delta E}

h ( Planck's\  constant) = 6.62 \times  10^{(-34)} \ Js \\\\ speed \ of \ light = 3 \times 10^{8} \ \frac{m}{s}\\\\= \frac{6.62 \times 10^{(-34)} \times 3 \times 10^ {8}}{2.18 \times  10^{-18}} (\frac{1}{4}- \frac{1}{81}) \\\\=3.83 \times 10^9 \ m\\\\

6 0
3 years ago
A rectangular field is 300 meters long and 300 meters wide. What is the area of the field in square kilometers? Do not round you
dexar [7]

Answer:

Area of the rectangular field in kilometers is 0.09 km^2

Explanation:

We know that 1 kilometers = 1000 meters

                    since we need to find the area in unit of kilometers

                    therefore converting length and width into kilometers

           1000 meters = 1 kilometers

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         Likewise  width  = 0.3 km

Area = length x width

         = 0.3km x 0.3 km

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6 0
3 years ago
If a soundproof door is almost shut but still leaves a small opening, what wave phenomenon is responsible for someone being able
lana66690 [7]

The phenomenon which is responsible for this effect is called diffraction.

Diffraction is the ability of a wave to propagate when it meets an obstacle or a slit. When the wave encounters the obstacle or the slit, it 'bends' around it and it continues propagate beyond it. A classical example of this phenomenon is when a sound wave propagates through a wall where there is a small aperture (as in the example of this problem)

5 0
3 years ago
Read 2 more answers
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