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grigory [225]
3 years ago
5

Provides most of the energy used in the world today.

Physics
1 answer:
lara [203]3 years ago
6 0

fossil fuels is used the most often in the world.

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Robert Hook discovered cells when viewing a _____ under a microscope.
sp2606 [1]
<span>What you need to do while answering this questions, is ask yourself what has cells - only if a thing has cells can you see those cells under a microscope. Objects of animal and plant origin have cells, so blood, plant and cork (made of tree bark) can have cells, and a box too, if it's made of wood. So we can''t exclude any answers based on this. We must then know the story of Robert Hook - and it was in fact a cork. He did this discovery around 1655. At the time his main interest was the microscope rather than the cork, and he used to cork to demonstrate the function of the microscope. The correct answer is CORK.</span>
3 0
4 years ago
Read 2 more answers
The battery charger for an mp3 player contains a step-down transformer with a turns ratio of 1:38, so that the voltage of 120 v
matrenka [14]
Transformer contains two coils: primary and secondary. They allow change of voltage to lower or higher value. In first case we have step-down and in second case we have step-up transformer.
Formula used for transformer is:\frac{N_{1} }{N_{2}} = \frac{V_{1}}{V_{2}}

Where:N1 = number of turns on primary coilN2 = number of turns on secondary coilV1 = voltage on primary coilV2 = voltage on secondary coil
In a step-down transformer primary coil has more turns than secondary coil. So the ratio 1:38 means that for each turn on secondary coil we have 38 turns on primary coil.
We can solve the equation for V2:V_{2} =  \frac{ V_{1}* N_{2}  }{ N_{1} }  \\  V_{2} =  \frac{ 120* x  }{ 38x} } \\ V_{2} = 3.16V

Secondary coil provides voltage of 3.16V.
7 0
3 years ago
4. A desk with a mass of 10 kg is pushed across a floor with an acceleration of 4 m/s?. What
tatiyna
40 N. If you’re using F=MA MxA would be 10x4 which would get you 40 N
6 0
3 years ago
Read 2 more answers
What do active solar heat systems have that passive systems do not have?.
tamaranim1 [39]

Answer:

Passive solar heating uses building design to utilize sunlight, while active solar heating uses technology.

Explanation:

lol

5 0
2 years ago
Uranium-235 decays to thorium-231 with a half-life of 700 million years. When a rock was formed, it contained 6400 million urani
Dahasolnce [82]

Answer:

proof in explanation

Explanation:

First, we will calculate the number of half-lives:

n = \frac{t}{t_{1/2}}

where,

n = no. of half-lives = ?

t = total time passed = 2100 million years

t_{1/2} = half-life = 700 million years

Therefore,

n = \frac{2100\ million\ years}{700\ million\ years}\\\\n = 3

Now, we will calculate the number of uranium nuclei left (n_u):

n_u = \frac{1}{2^{n} }(total\ nuclei)\\\\n_u = \frac{1}{2^{3} }(6400\ million)\\\\n_u = \frac{1}{8}(6400\ million)\\\\n_u =  800\ million

and the rest of the uranium nuclei will become thorium nuclei (u_{th})

n_{th} = total\ nuclei - n_u\\n_{th} = 6400\ million-800\ million\\n_{th} = 5600\ million

dividing both:

\frac{n_{th}}{n_u}=\frac{5600\ million}{800\ million} \\\\n_{th} = 7n_u

<u>Hence, it is proven that after 2100 million years there are seven times more thorium nuclei than uranium nuclei in the rock.</u>

6 0
3 years ago
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