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3 years ago

Help me please :(((((((

Physics

2 answers:

Dimas [21]3 years ago

5 0

Answer: A.

Explanation: Roughly 180 - 200 million years ago, just before the first dinosaurs evolved. Mammals themselves evolved from a group or reptiles which exhibited mammal-like traits. One of them was specialized teeth. Reptiles tend to have teeth all the same shape. The mammal-like reptiles evolved tiny teeth in front of the jaw and two pairs of over sized fangs along the the sides. Like modern mammals, the head was large in proportion to the rest of the body. The jaws were also evolving another mammal trait, the ability to move sideways. Despite the lack of specialized teeth, acute hearing and the ability to chew, the dinosaurs evolved an adaptation which made them far more successful than mammals--modified leg bones. These limbs could be articulated directly under their bodies. This enabled the legs to support more weight, since the limbs were now under the body instead of at the sides. Then dinosaurs did something which secured their dominance for the next 120 million years - they began to stand on two legs. Although the back was still parallel to the ground, running on two legs greatly increased the dinosaur's speed. Mammals could simply not compete with swift, giant predators and were forced to remain small, and most became nocturnal to evade dinosaurs which were probably active during the day. Despite that they managed to survive which allowed the further evolution of mammals into us, humans.

sveta [45]3 years ago

5 0

In the Cenozoic period only mammals were alive. All dinosaurs had gone extinct leaving animals such as cave lions, woolly mammoths, and cave bears. Considering that Dinosaurs had gone extinct roughly 66 million years ago in the Cretaceous era and the Cenozoic era was 66 million years ago, the beginning of the Cenozoic era started with the extinction of dinosaurs.

Answer: D

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pashok25 [27]

A) initial volume
We can calculate the initial volume of the gas by using the ideal gas law:
$p_i V_i = nRT_i$
where
$p_i=1.0 atm=1.01 \cdot 10^5 Pa$ is the initial pressure of the gas
$V_i$ is the initial volume of the gas
$n=2.3 mol$ is the number of moles
$R=8.31 J/K mol$ is the gas constant
$T_i=240^{\circ}C=513 K$ is the initial temperature of the gas

By re-arranging this equation, we can find $V_i$ :
$V_i = \frac{nRT_i}{p_i} = \frac{(2.3 mol)(8.31 J/mol K)(513 K)}{1.01 \cdot 10^5 Pa}=0.097 m^3$

2) Now the gas cools down to a temperature of
$T_f = 14^{\circ}C=287 K$
while the pressure is kept constant: $p_f = p_i = 1.01 \cdot 10^5 Pa$ , so we can use again the ideal gas law to find the new volume of the gas
$V_f = \frac{nRT_f}{p_f}= \frac{(2.3 mol)(8.31 J/molK)(287 K)}{1.01 \cdot 10^5 Pa} = 0.054 m^3$

3) In a process at constant pressure, the work done by the gas is equal to the product between the pressure and the difference of volume:
$W=p \Delta V= p(V_f -V_i)$
by using the data we found at point 1) and 2), we find
$W=p(V_f -V_i)=(1.01 \cdot 10^5 Pa)(0.054 m^3-0.097 m^3)=-4343 J$
where the negative sign means the work is done by the surrounding on the gas.

5 0

3 years ago

The current through a 10 ohm resistor is 1.2 amperes.What is the potential difference across the resistor?

Natalija [7]

<u>Answer</u>: The potential difference across the resistor is 12 volts.

<u>Explanation:</u>

To calculate the potential difference cross the resistor, we use Ohm's Law. This law states that the potential difference across two wires is directly proportional to the current flowing through that wire.

Mathematically,

$V\propto I\\V=IR$

Where,

V = potential difference = ?V

I = Current flowing = 1.2 A

R = Resistor = $10\Omega$

Putting values in above equation, we get:

$V=1.2\times 10=12V$

Hence, the potential difference across the resistor is 12 volts

6 0

3 years ago

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Aleksandr-060686 [28]

Answer:

I guess that the atoms are:

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Neutrons: 8 8 5 3 13 14

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From the given options, the only two that have the same number of protons but a different number of neutrons are:

Protons 12, neutrons 13

and

Protons 12, neutrons 14.

These two are isiotopes.

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3 years ago

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Dmitriy789 [7]

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JulsSmile [24]

Answer is 76,352 just look it up

8 0

2 years ago

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