Structure Of Nucleus

• It is generally the most prominent organelle in the cell.
• The nucleus is completely bound by membranes.
• It is surrounded by a structure called the nuclear envelope.
• This membrane separates the contents of the nucleus from the cytoplasm.
• The cell’s chromosomes are also enclosed within it.
• DNA is present in the Chromosomes and they provide the genetic information required for the creation of other cell components and also for reproduction of life.

Cell was first discovered by Robert Hooke in 1665. He discovered plant cells by viewing the cell walls in its cork tissue under a microscope. He described the cell as the basic unit of life.

The cell was first discovered by Robert Hooke in 1665, which can be found to be described in his book Micrographia. In this book, he gave 60 'observations' in detail of various objects under a coarse, compound microscope.

Meiosis is a type of cell division that results in the formation of four daughter cells each with half the number of chromosomes as the parent cell.
Mitosis is the type of cell division that results in the formation of two daughter cells each with the same number of chromosomes as the parent cell.

There are two principles for treatment of infectious diseases:

Reducing the effect of a disease: In this method, the side-effects or symptoms of a disease are reduced, which are usually because of inflammation. This includes taking medicines to bring down fever, reduce pain etc. One can take rest to save energy so that the body can focus on healing. However, this kind of treatment does not cure a disease as it does not kill the micro-organism that causes the disease.

Killing the cause of a disease: It includes taking microbe-specific medicines. Microbes are classified into virus, bacteria, fungus, protozoa etc. Each group of these microbes have some essential biochemical process which is specific to its group and is not shared by any other group of microbes. Hence, medicines which are specific for that group are prescribed.

Acceleration

• Acceleration: It is a measure of the change in the velocity of an object per unit time.
• Acceleration can be caused either by change in direction of motion or change in speed or both. 
  Acceleration = Change in velocity/ time taken

Following are the three types of inertia:
Inertia of Rest: When the resistance is offered by the body to continue in the state of rest unless an external force acts on it.

Inertia of Direction: When the resistance is offered by the body to continue the motion in the same direction unless an external force acts on it.
Inertia of Motion: When the resistance is offered by the body to continue to be in the uniform motion unless an external force acts on it.

Consider the linear motion of a body with an initial velocity u. Let the body accelerate uniformly and acquire a final velocity v after time t. The velocity–time graph is a straight line AB as shown below.

At t = 0, initial velocity = u = OA 

At t = t, final velocity = v = OC

The distance S travelled in time t = area of the trapezium OABD

s = (1/2) x (OA + DB) × OD

s = (1/2) x (u + v) × t  

Since v = u + at,

s = (1/2) x (u + u + at) × t

s = ut + (1/2) at²

Direction of force means that the force acts in the same direction in which the force is applied and force is also a vector quantity  The SI unit of force is newton (N)

The direction of an arrow shows the direction of the force, and the length of the arrow indicates the amount, or size, of the force.

Kinetic energy is the energy possessed by a body by virtue of its motion. All moving bodies have kinetic energy. A body of mass m moving with a velocity v has a kinetic enegy E = ½ mv².  Note that kinetic energy is always positive.

Alternately we can define K.E as follows.
The work done by a body by virtue of its motion is called kinetic energy.

By increasing the temperature (by heating), a solid can be converted into liquid state, and the liquid can be converted into gaseous state. By decreasing the temperature (by cooling), a gas can be converted into liquid state, and a liquid can be converted into solid state.

1. Solid to Liquid Change: Melting

On increasing the temperature of solids, the kinetic energy of the particles increases. Due to the increase in kinetic energy, the particles start vibrating with greater speed. The energy supplied by heat overcomes the forces of attraction between the particles. The particles leave their fixed positions and start moving more freely. A stage is reached when the solid melts and is converted to a liquid. The temperature at which a solid melts to become a liquid at the atmospheric pressure is called its melting point. The amount of heat energy that is required to change 1 kg of a solid into liquid at atmospheric pressure at its melting point is known as the latent heat of fusion. So, particles in water at 0o C (273 K) have more energy as compared to particles in ice at the same temperature.

1. Liquid to Gas Change: Boiling (Vaporisation)

The process in which a liquid substance changes into a gas rapidly on heating, is called boiling. When we supply heat energy to water, particles start moving even faster. At a certain temperature, a point is reached when the particles have enough energy to break free from the forces of attraction of each other. At this temperature the liquid starts changing into gas. The temperature at which a liquid starts boiling at the atmospheric pressure is known as its boiling point. Particles in steam, that is, water vapour at 373 K (100o C) have more energy than water at the same temperature because particles in steam have absorbed extra energy in the form of latent heat of vaporisation.

1. Gas to Liquid Change: Condensation

The process of change of gas to a liquid by cooling, is called condensation. When a gas is cooled enough, then its particles lose so much kinetic energy that they slow down, move closer together until they start being attracted to each other, and form a liquid. Condensation is the reverse process of boiling.

1. Liquid to Solid Change: Freezing

The process of changing a liquid into a solid by cooling, is called freezing. Freezing means solidification. Freezing is the reverse of melting. When a liquid is cooled, its particles lose energy due to which they lose slowly. If the liquid is cooled enough, its each particle stops moving and vibrate about a fixed position.

Layers of the Sun

• Solar interior composed of core (which occupies the innermost quarter or so of the radius),
• The radiative zone,
• The convective zone,
• There is the visible surface known as the photosphere,
• The chromosphere,
• The outermost layer, the corona.

Cells are made up of components called cell organelles.

A cell is capable to live and perform all their respective functions due to the presence of cell organelles.

All cells have the same organelles irrespective of their function and organism they are found in i.e. let it be a bone cell or a nerve cell or any other cell, all will have components.

Final Velocity (v) = 15km/hr
Initial Velocity (u) = 10km/hr
Time = 6 seconds
Acceleration = ?

According to Formula :

Acceleration = v – u / t

Acceleration = 15km – 10km / 6 seconds

Acceleration = 15000m – 10000m / 6 seconds

[we will convert smaller units into bigger units. because in time we have smaller unit and here we cant convert time in hours or minute because it is only 6.]

Acceleration = 5000m / 6 seconds

[ means that we will divide 5000 by 6 . You acn also use cancellation method]

Acceleration = 833.333333

Fluidity is the quality or state of being fluid. It is the ability of a substance to flow easily. The most common example of a high fluid Material is water, as it has less force of attraction between the molecules. Fluidity is the property of a fluid which allows fluid to flow. That means as high the fluidity, more easily fluid can flow. (means if the viscosity of the fluid is more, it's internal resistance between layers will high so can't flow easily).

Fluidity : It is the property by virtue of which, the particles of a molecule move in space. A substance whose particles can move easily is said to be fluid, for example, liquid.

Fluidity: The physical property of a substance that enables it to flow is called fluidity. In solids – Very low In liquids – Higher than in solids but lower than in gases In gases – Very high 

Consider the linear motion of a body with an initial velocity u. Let the body accelerate uniformly and acquire a final velocity v after time t. The velocity–time graph is a straight line AB as shown below.

At t = 0, initial velocity = u = OA 

At t = t, final velocity = v = OC

The distance S travelled in time t = area of the trapezium OABD

s = (1/2) x (OA + DB) × OD

s = (1/2) x (u + v) × t  

Since v = u + at,

s = (1/2) x (u + u + at) × t

s = ut + (1/2) at²  

The waves suffer multiple reflections from the walls, ceilings and other materials present, when a sound is produced in a big hall or auditorium. As a result of this, sound persists for some time even after the source has stopped producing sound.
Revertebration is the process of persistence of sound due to repeated reflection. 

Methods of reducing reverberation.

In a big hall or auditorium, excessive reverberation is highly undesirable. The following below methods can be used to reduce them.

(i) By covering the walls and roof of the auditorium with sound absorbent materials like compressed fireboard, rough plaster, etc.

(ii) Providing open windows in the space.

(iii) Providing heavy curtains with folds, so that the sound gets absorbed. 

(iv) By using good sound absorbing materials for the seats.