Answer:
the reason paper airplanes fly is because of lift the foil has no lift
Explanation:
Answer:
Explanation: All real solids are impure. A very high purity material, say 99.9999% pure. Impurities are often added to materials to improve the properties. For instance, carbon added in small amounts to iron makes steel, which is stronger than iron. Boron impurities added to silicon drastically change its electrical properties.
The properties of materials are profoundly influenced by the presence of imperfections.
TYPES OF IMPURITIES
1. Point defects
• Vacancy atoms (vacant atomic sites in a structure causing a distortion of planes). They are common, especially at high temperatures when atoms are frequently and randomly change their positions leaving behind empty lattice sites. In most cases diffusion (mass transport by atomic motion) can only occur because of vacancies.
• Self-Interstitial atoms ("extra" atoms positioned between atomic sites causing a distortion of planes) A self interstitial atom is an extra atom that has crowded its way into an interstitial void in the crystal structure. Self interstitial atoms occur only in low concentrations in metals because they distort and highly stress the tightly packed lattice structure.
2. Impurities:
- Substitutional (mpurity atom in lattice). Substitutional impurity atoms are usually close in size (within approximately 15%) to the bulk atom. An example of substitutional impurity atoms is the zinc atoms in brass. In brass, zinc atoms with a radius of 0.133 nm have replaced some of the copper atoms, which have a radius of 0.128 nm.
- Interstitial atoms (impurity atom not in regular lattice sit) . An example of interstitial impurity atoms is the carbon atoms that are added to iron to make steel. Carbon atoms, with a radius of 0.071 nm, fit nicely in the open spaces between the larger (0.124 nm) iron atoms.
3.
Line defects
• Dislocations
4. Area defects
• Grain Boundaries
Answer: 100% (double)
Explanation:
The question tells us two important things:
- Mass remains constant
- Volume remains constant
(We can think in a gas enclosed in a closed bottle, which is heated, for instance)
In this case we know that, as always the gas can be considered as ideal, we can apply the general equation for ideal gases, as follows:
- State 1 (P1, V1, n1, T1) ⇒ P1*V1 = n1*R*T1
- State 2 (P2, V2, n2, T2) ⇒ P2*V2 = n2*R*T2
But we know that V1=V2 and that n1=n2, som dividing both sides, we get:
P1/P2 = T1/T2, i.e, if T2=2 T1, in order to keep both sides equal, we need that P2= 2 P1.
This result is just reasonable, because as temperature measures the kinetic energy of the gas molecules, if temperature increases, the kinetic energy will also increase, and consequently, the frequency of collisions of the molecules (which is the pressure) will also increase in the same proportion.
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