Answer:
The electrons in an atom can only occupy certain allowed energy levels. ... Only certain energy levels are allowed, so only certain transitions are possible and hence specific wavelengths are emitted when an electron drops to a lower energy level.
In most compartment fires, the energy release in fire is directly proportional to the amount of oxygen available for combustion.
Answer: Option B
<u>Explanation:</u>
A fire is the chemical outcome of energy generated by the heat. So, this heat is generating fire due to friction between the heating source with igniting elements. And to increase the chain reaction of fire leading to combustion or fire require oxygen. So, the amount of oxygen will lead to the production of fire. Thus, the energy released by fire will be equal to the amount of oxygen available for combustion.
If there is no oxygen, then the fire will get succumbed. The fire consumes the oxygen present to increase the pace and spread of fire. So the consumed oxygen utilized for converting the simple fire to combustion will be equal to the release of energy in fire. Thus, energy released in fire is directly proportional to the amount of oxygen available for combustion.
Answer:
<em>Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.</em>
Explanation:
<u>Potential and Kinetic Energy</u>
The gravitational potential energy is the energy an object has due to its height above the ground. The formula is

Where:
m = mass of the object
g = acceleration of gravity (9.8~m/s^2)
h = height
Note we can also use the object's weight W=mg into the formula:

The kinetic energy is the energy an object has due to its speed:

Where v is the object's speed.
Initially, the object has no kinetic energy because it's assumed at rest.
The W=30 N rock falls from a height of h=40 m, thus:

Since the sum of the kinetic and potential energies is constant:
U' + K' = 1,200 J
Here, U' and K' are the energies at any point of the motion. Since both must be the same:
U' = K' = 600 J
U'=Wh'=600
Solving for h':

Both energies are equal when the rock has fallen 20 m or equivalently when it is at a height of 20 m.
Answer:
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-- Kinetic energy is the energy of mass in motion. The amount is determined by the mass of whatever is moving, and its speed.
-- Potential energy is the energy that's stored up in some form, not being used yet but ready to be used when you want it.
For example, one form of it is <u><em>chemical</em></u><em> </em>potential energy, like in a battery, or a match. You get the energy out of a battery when you connect it to a motor or a light. You get the energy out of as match when you make the tip hot and it flares up.
This question is asking about <u><em>gravitational</em></u> potential energy. An object has stored energy just by being up high, like a bowling ball on a shelf. You get the energy out of it just by dropping it ... possibly enough to crack the floor !
The amount of this kind of potential energy is determined by the mass of the object, and how high up it is.
-- Getting the answers from other people doesn't help you a bit, until you understand them and can answer the question on your own.