As the humidity increases, so too does the percentage of air molecules that are water molecules. ... Lower density translates into faster sound wave travel, so sound waves travel faster at high humidity. The increase in speed, however, is very small, so for most everyday purposes you can ignore it.The speed of sound is affected by temperature and humidity. Because it is less dense, sound passes through hot air faster than it passes through cold air. ... Dry air absorbs far more acoustical energy than does moist air. This is because moist air is less dense than dry air (water vapor weighs less than air).

The speed of sound also depends on the temperature of the medium. The hotter the medium is, the faster its particles move and therefore the quicker the sound will travel through the medium. When we heat a substance, the particles in that substance have more kinetic energy and vibrate or move faster. Sound can therefore be transmitted more easily and quickly in hotter substances.

According to the second law of motion, force is the product of mass and acceleration. Suppose the mass of the stone be m. The acceleration involved in falling objects due to the gravitational force and is denoted by g.

Therefore the magnitude of the gravitational force F will be equal to the product of mass and acceleration due to the gravitational force, that is,

F = m g                                                                                                                                 ii.

From Eqs. i. and ii.  we have

m g = G M x m/d²

Or g = GM /d²

where M is the mass of the earth, and d is the distance between the object and the earth.

Let an object be on or near the surface of the earth. The distance d will be equal to R, the radius of the earth. Thus, for objects on or near the surface of the earth,

mg = = G M x m/r²

g = GM /r²

To Calculate the Value of g:

To calculate the value of g, we should put the value of universal gravitational constant, G = 6.673 × 10^–11 N m² kg^–2; mass of the earth, M = 6 x 10²⁴ kg; and radius of earth R = 6.4 x 10⁶ m in the given equation:

g = GM /r²

g = 6.673 × 10^–11 N m² kg^–2 x 6 x 10²⁴ kg/(6.4 x 10⁶ m)² = 9.8 m/s²

Thus, the value of acceleration due to gravity of the earth, g = 9.8 m s^–2.

Every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.

Suppose two bodies A and B of masses M and m are lying at a distance d from each other. Let the force of attraction between these two bodies be F. according to the universal law of gravitation;

1. The force between the two bodies is directly proportional to the product of their masses.

F ∝ M × m

1. The force between the two bodies is inversely proportional to the square of the distance between them.

F ∝ 1/d²

Combining both the equations:

F ∝ M x m/d²

Or F = G M x m/d²                                                                                                           i.

where G is the constant of proportionality and is called the universal gravitation constant.

By multiplying crosswise we get

 F × d² = G M × m

Or G = F d²/ M x m

The SI unit of G can be obtained by substituting the units of force, distance and mass as N m² kg ^–2.

The value of G was found out by Henry Cavendish (1731 – 1810). The accepted value of G is 6.673 × 10^–11 N m² kg^–2.

This equation gives the magnitude of the force and since it is an attractive force it will always be directed towards the other object. From the above equation, we can come to the conclusion that anything that has mass has gravity. Objects with heavier mass have more gravity. The closer the two objects are, the heavier the gravitational pull between them. Gravity gets weaker with distance.

Yes, time goes faster the farther away you are from the earth's surface compared to the time on the surface of the earth. This effect is known as "gravitational time dilation". It is predicted by Einstein's theory of General Relativity and has by verified multiple times by experiments. Gravitational time dilation occurs because objects with a lot of mass create a strong gravitational field. The gravitational field is really a curving of space and time. The stronger the gravity, the more spacetime curves, and the slower time itself proceeds. We should note here, however, that an observer in the strong gravity experiences his time as running normal. It is only relative to a reference frame with weaker gravity that his time runs slow. A person in strong gravity therefore sees his clock run normal and sees the clock in weak gravity run fast, while the person in weak gravity sees his clock run normal and the other clock run slow. There is nothing wrong with the clocks. Time itself is slowing down and speeding up because of the relativistic way in which mass warps space and time.

The size of the particles which make up matter are very, very small. This can be shown  by  performing the given experiment:

i. Take 2-3 crystals of potassium permanganate and dissolve them in 100 mL of water.

ii. Take out approximately 10 mL of this solution and put it into 90 mL of clear water.

iii. Take out 10 mL of this solution and put it into another 90 mL of clear water.

iv. Keep diluting the solution like this 5 to 8 times.

This experiment shows that just a few crystals of potassium permanganate can colour a large volume of water (about 1000 L). So we conclude that there must be millions of tiny particles in just one crystal of potassium permanganate, which keep on dividing themselves into smaller and smaller particles.

Upon increasing temperature the kinetic energy of the particles increases, as a result the particles start moving with high speed and intermix more rapidly with each other and so the rate of diffusion increases with heating.

Rough Endoplasmic Reticulum (RER) : It helps in the formation of lysosomes

Smooth Endoplasmic Reticulum (SER) : Gives rise to sphareosomes.

Cyanobacteria are prokaryotic cells that lack membrane-bound organelles and nuclei. Their common name is blue-green algae because of their blue-green color brought on by their pigment phycocyanin. Most algae are considered plants, but blue-green algae are bacteria.

Induction is the magnetic field which is proportional to the rate of change of the magnetic field. This definition of induction holds for a conductor. Induction is also known as inductance. L is used to represent the inductance and Henry is the SI unit of inductance.

1 Henry is defined as the amount of inductance required to produce an emf of 1 volt in a conductor when the current change in the conductor is at the rate of 1 Ampere per second.

Pathogens

One of the most severe pollutants is the disease-causing microorganisms called pathogens. Pathogens are mostly bacteria, virus, and protozoa. Although bacteria are considered harmless if not beneficial, there are a few of pathogenic bacteria as well which enter the water bodies through sewers and sanitation systems. The water-borne pathogens cause several diseases such as diarrhea, gastrointestinal illness, etc.

  Organic Wastes

Organic water pollutants include food waste, detergents, leaves, grass, etc. They originate from domestic sewage, discharge from food processing factories and farm wastes which reach the water sources through runoff and pollute them. It is a fact that the bacteria decompose the complex organic matter into the simple organic matter. They consume oxygen which is dissolved in water. As the organic waste content in the water increases so does the count of decomposers. They use up a lot of oxygen which results in the depletion of oxygen content in water. This adversely affects the aquatic life.

The major causes of the greenhouse effect are:

Burning of Fossil Fuels: Fossil fuels are an important part of our lives. They are widely used in transportation and to produce electricity. Burning of fossil fuels releases carbon dioxide. With the increase in population, the utilization of fossil fuels had increased. This has led to an increase in the release of greenhouse gases in the atmosphere.

Deforestation: Plants and trees take in carbon dioxide and release oxygen. Due to the cutting of trees, there is an inconsiderable increase in the greenhouse gases which increases the earth’s temperature.

Farming: Nitrous oxide used in fertilizers is one of the contributors to the greenhouse effect in the atmosphere.

Industrial Waste and Landfills:  The industries and factories produce harmful gases which are released in the atmosphere. Landfills also release carbon dioxide and methane that adds to the greenhouse gases.

It is one of the fundamental quantities in Physics and the most basic property of matter. We can define mass as the measure of the amount of matter in a body. The SI unit of mass is Kilogram (kg).

Matter is defined as that which has mass and occupies space. It is indeed made of particles. Space is that which is occupied by matter. So, any definition of space exists only if there is matter. All matter is particulate in nature. This means there are spaces which has no matter between the bits of matter. This is called the “atomic nature of matter."