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3 years ago

• How were historical solar system models different from our current model?

1 answer:

4 0

One of the most famous historical model was the geocentric model thought of by plato. This model says that the earth is in the center of the universe and that each of the planets follow complicated paths that go backwards sometimes. This model was used until a new one was accepted. This model is the one we have today called the heliocentric model. It was bought of by Copernicus. Hope that answers your question!

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Two examples of chemical reactions that involved a thermal energy change:

zzz [600]

Answer:

Option 1 is endothermic

Option 2 is exothermic

Explanation:

In Chemistry, Exothermic reactions are reactions whereby heat energy is transferred to the surroundings and the temperature of the surroundings increases. Endothermic reactions are those whereby heat energy from the surroundings is absorbed and thereby making the temperature of the surroundings to decrease.

This means in simple terms that endothermic reactions will have heat on the reaction side of the equation while exothermic will have heat on the product side of the equation.

Thus;

Option 1 is endothermic since it has heat absorbed on the reactant side.

Option 2 is exothermic since it gives off heat on the product side.

6 0

2 years ago

um can someone please help me I'm really stuck on this question and an explanation would be nice thank you

masha68 [24]

Answer: A wavelength is how long ONE wave is. First divide the distance of the whole diagram by the number of waves. you will get 2m. This is the answer.

6 0

2 years ago

23.

Volgvan

Answer:

1 m = 100 cm....so 2.5 m = (2.5 * 100) = 250 cm

a = 1st shelf

b = 2nd

c = 3rd

d = 4th

a + b + c + d = 250

b = 2a + 18

c = a - 12

d = a + 4

a + (2a + 18) + (a - 12) + (a + 4) = 250

5a + 10 = 250

5a = 250 - 10

5a = 240

a = 240/5

a = 48 cm <== 1st shelf

b = 2a + 18 = 2(48) + 18 = 114 cm <== 2nd shelf

c = a - 12 = 48 - 12 = 36 cm <== 3rd shelf

d = a + 4 = 48 + 4 = 52 cm <== 4th shelf

so 2nd shelf is 114 cm

4 0

2 years ago

How much energy was released if rocket hydrogen fuel was burnt ?

suter [353]

When ignited, the gas mixture converts to water vapor and releases energy, which sustains the reaction: 241.8 kJ of energy (LHV) for every mole of H2 burned.” A mole of hydrogen weighs 2 grams. So, this is a LHV (lower heating value) of 120.9 kJ/gram of hydrogen when heat of vaporization is subtracted.

6 0

2 years ago

Read 2 more answers

An unstable particle is created in the upper atmosphere from a cosmic ray and travels straight down toward the surface of the ea

german

Answer:

Q1) Time taking by particle to travel the 40 km wrt. earth = $1.34\times10^{-6}$ sec.