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4 years ago

Why do helium-filled balloons float in air?

2 answers:

8 0

A helium balloon displaces the amount of air. The weight of the helium in the balloon + the balloon fabric = lighter than the air that it displaces. Helium is lighter than air, so therefore, if it's in a balloon, the balloon will float.

kati45 [8]4 years ago

7 0

The helium balloon displaces an amount of air. As long as the weight of the helium plus the balloon fabric is lighter than the air it displaces, the balloon will float in the air. It turns out helium is a lot lighter than air.

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19. Which of the following best describes the role of the spark from the spark plug in an automobile engine?

sergey [27]

The role of a spark plug is to supply some of the energy of activation for the combustion reaction.

<u>Explanation:</u>

A Spark plug is a tiny bolt of lightning in which a spark of electricity is emitted across a gap creating the ignition of the combustion chamber thereby starting the engine. By putting an engine piston in motion we can power up which produces a smooth burn of the compressed air-fuel mixture.

An electrical device that fits into the cylinder head and ignites compressed aerosol gasoline by an electric spark. They have an insulated electrode connected to a coil that ignites thereby producing sparks.
The spark plug works as a heat exchanger. They tend to pull unwanted thermal energy from the combustion chamber and heat is transferred to the engine's cooling system. Thus they supply some of the energy for the activation of engines.

4 0

3 years ago

If a radioactive material has a 10 year half-life, how much of a 100 g sample will be left after 30 years?

olga_2 [115]

12.5g, each 10 years you lose a half of what you have at that given moment

5 0

3 years ago

If the detector is capturing 3.3×108 photons per second at this wavelength, what is the total energy of the photons detected in

Reil [10]

Answer:

The total energy of the photons detected in one hour is 7.04*10⁻¹¹ J

Explanation:

The energy carried by electromagnetic radiation is displaced by waves. This energy is not continuous, but is transmitted grouped into small "quanta" of energy called photons. The energy (E) carried by electromagnetic radiation can be measured in Joules (J). Frequency (ν or f) is the number of times a wave oscillates in one second and is measured in cycles / second or hertz (Hz). The frequency is directly proportional to the energy carried by a radiation, according to the equation: E = h.f, (where h is the Planck constant = 6.63 · 10⁻³⁴ J / s).

Wavelength is the minimum distance between two successive points on the wave that are in the same state of vibration. it is expressed in units of length (m). In light and other electromagnetic waves that propagate at the speed of light (c), the frequency would be equal to the speed of light (≈ 3 × 10⁸ m / s) between the wavelength :

$f=\frac{speed of light}{wavelength}$

So:

$E=\frac{h*speed of light}{wavelength}$

In this case, the wavelength is 3.35mm=3.35*10⁻³m and the energy per photon is:

$E=\frac{6.63*10^{-34}*3*10^{8}}{3.35*10^{-3} }$

E=5.93*10⁻²³ $\frac{J}{proton}$

The detector is capturing 3.3*10⁸ photons per second. So, in 1 hour:

$E=5.93*10^{-23} \frac{J}{proton} *3.3*10^{8} \frac{proton}{s} *\frac{60}{1} \frac{s}{minute} *\frac{60}{1} \frac{minute}{hr}$

E=7.04*10⁻¹¹ $\frac{J}{hr}$

The total energy of the photons detected in one hour is 7.04*10⁻¹¹ J

3 0

3 years ago

In the redox conversion of Ni2+ to NiO4−, the oxidation number of Ni goes from (−2, 0, +2) to (−1, +1, +7, +9). Recall that the

inessss [21]

Oxidation number of an atom is the charge that atom would have if the compound is composed of ions. In neutral substances that contains atoms of one element the oxidation number of an atom is zero. Thus atoms in O2, Ni2, and aluminium all have oxidation number of zero.
In this case, Ni2, the oxidation number of Ni atom is zero,
for NiO4-, assuming oxidation number of Ni is x
(x ×1) + (-2 × 4) = -1
x = + 7
Therefore, the oxidation number goes from 0 to +7

7 0

3 years ago

How do the test variables (independent variables) and outcome variables (dependent variables) in an experiment compare? A. The t

Ghella [55]

Answer:

I'm on the exact same queston

6 0

3 years ago

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