Question
The third law of motion states that when one object exerts a force on another object, the second object instantaneously exerts a force back on the first. These two forces are always equal in magnitude but opposite in direction. These forces act on different objects and neveron the same object. It is important to note that even though the action and reaction forces are always equal in magnitude; these forces may not produce accelerations of equal magnitudes, this is because each force acts on a different object that may have a different mass.The two opposing forces are also known as action and reaction forces. Answer the following questions.
(i) Action reaction forces are always
$(a)$ Equal and in same direction
$(b)$ Equal and in opposite direction
$(c)$ Unequal and in same direction
$(d)$ None of the above
(ii) Which of the following is correct about action reaction forces?
$(a)$ They act on different objects
$(b)$ They are equal in magnitude and opposite in direction
$(c)$ Both forces acted on different object simultaneously
$(d)$ All the above
(iii) State third law of motion
(iv) Give 5 examples of third law of motion
(v) Even though the action and reaction forces are always equal in magnitude; these forces may not produce accelerations of equal magnitudes. Give your justification on this statement

Answer

$(i) b$
$(ii) d$
$(iii)$ The third law of motion states that when one object exerts a force on another object, the second object instantaneously exerts a force back on the first. These two forces are always equal in magnitude but opposite in direction. These forces act on different objects and neveron the same object.
$(iv)$ Examples of third law of motion are
  • Swimming or rowing a boat.
    Static friction while pushing an object.
    Walking.
    Standing on the ground or sitting on a chair.
    The upward thrust of a rocket.
    Resting against a wall or tree.
$(v)$ Even though the action and reaction forces are always equal in magnitude; these forces may not produce accelerations of equal magnitudes because these action reaction forces are acting on two different objects having different masses that’s why they are acceleration with different magnitude.

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Meristematic tissue take up a specific role and lose the ability to divide. As a result, they form a permanent tissue. This process of taking up a permanent shape, size, and a function is called differentiation. Differentiation leads to the development of various types of permanent tissues.
Simple Permanent Tissue
Tissue made of one type of cells, which look like each other. Such tissues are called simple permanent tissue. Parenchyma is the most common simple permanent tissue. It consists of relatively unspecialised cells with thin cell walls. They are living cells. They are usually loosely arranged, thus large spaces between cells (intercellular spaces) are found in this tissue. This tissue generally stores food. In some situations, it contains chlorophyll and performs photosynthesis, and then it is called chlorenchyma. In aquatic plants, large air cavities are present in parenchyma to help them float. Such a parenchyma type is called aerenchyma.Yet another type of permanent tissue is sclerenchyma. It is the tissue which makes the plant hard and stiff. We have seen the husk of a coconut. It is made of sclerenchymatous tissue. The cells of this tissue are dead. They are long and narrow as the walls are thickened due to lignin.
Simple Permanent Tissue
Complex tissues are made of more than one type of cells. All these cells coordinate to perform a common function. Xylem and phloem are examples of such complex tissues. They are both conducting tissues and constitute a vascular bundle. Xylem fibres are mainly supportive in function. Phloem transports food from leaves to other parts of the plant. Except phloem fibres, other phloem cells are living cells.
(1) Tissue made of only one type of cell is termed as _________
$(a)$ Simple permanent tissue
$(b)$ Complex permanent tissue
$(c)$ Simple Meristematic tissue
$(d)$ Complex Meristematic tissue
(2) Xylem and phloem are examples of
$(a)$ Meristematic tissue
$(b)$ Simple tissue
$(c)$ Protective tissue
$(d)$ Complex tissue
(3) In aquatic plants, which type of parenchymatissue is found?
$(a)$ Aerenchyma
$(b)$ Chlorenchyma
$(c)$ Sclerenchyma
$(d)$ Parenchyma
(4) What is mean by Differentiation?
(5) Enlist the type of parenchyma tissue.
When the solid A is added to water, it dissolves with the evolution of a lot of heat and making little explosions to form two products $B$ and $C$. The properties of products $B$ and $C$ are entirely different from those of solid $A$ as well as water. Moreover, products $B$ and $C$ cannot be reconverted into solid $A$ and water. When another solid $D$ is added to water, it dissolves with the absorption of a little heat to form a product E which cools down. The product $E$ shows the properties of both, solid $D$ as well as water. Moreover, product $E$ can be converted into solid $D$ and water.
$a.$ What type of change occurs when solid $A$ is dissolved in water? Why?
$b.$ What type of change occurs when sold $D$ is dissolved in water? Why?
$c.$ Name a metal which you think could behave like solid A. Also name the products $B$ and $C.$
$d.$ Name the solid $D$ if it is the one which is used in making ordinary dry cells.
$e.$ Name the process by which $D$ can be recovered from $E$.
Every object in the universe attracts every other object with a force which is proportional to the product of their masses ($m1*m2$) and inversely proportional to the square of the distance ($d^2$) between them. The force is along the line joining the centers of two objects.

(i)Gravitational force does not depend on
$(a)$ Masses of objects
$(b)$ Separation between objects
$(c)$ Charges on objects
$(d)$ None of these
(ii) Force of gravitation varies with masses of object as
$(a)$ Product of masses
$(b)$ Sum of masses
$(c)$ Difference of masses
$(d)$ None of these
(iii) When mass of one body is doubled then force of gravitation will become
$(a)$ Force will remain same
$(b)$ Force will become double
$(c)$ Force will become halved
$(d)$ None of these
(iv)What is universal gravitational constant? What is its SI unit?
(v) Two objects of masses 10kg and 20kg separated by distance 10m. What is gravitational force between them?
Work done by force acting on an object is equal to the magnitude of the force multiplied by the distance moved in the direction of the force. Work has only magnitude and no direction. Work done is negative when the force acts opposite to the direction of displacement. Work done is positive when the force is in the direction of displacement.The unit of work is newton-metre ($N$ m)or joule $(J)$.
(i) Work done is
$(a)$ Scalar quantity
$(b)$ Vector quantity
$(c)$ Tensor quantity
$(d)$ None of these
(ii) When force acts against the direction of displacement then work done will be
$(a)$ positive
$(b)$ negative
$(c)$ both a and b can possible
$(d)$ None of these
(iii) SI unit of work is
$(a)$ Joule$(J)$
$(b)$ Newton meter$(N-m)$
$(c)$ both $a$ and $b$
$(d)$ None of these
(iv)You are lifting stone from floor. Work is done by theforce exerted by you on the stone. Theobject moves upwards. The force youexerted is in the direction ofdisplacement. However, there is theforce of gravity acting on the object. Which one of these forces is doingpositive work?
Which one is doing negative work?
(v) Define 1J of work.
Elemental oxygen is normally found in the form of a diatomic molecule. However, in the upper reaches of the atmosphere, a molecule containing three atoms of oxygen is found. This would mean a formula of $O3$ and this is called ozone. Unlike the normal diatomic molecule of oxygen, ozone is poisonous and we are lucky that it is not stable nearer to the Earth’s surface. But it performs an essential function where it is found. It absorbs harmful radiations from the Sun. This prevents those harmful radiations from reaching the surface of the Earth where they may damage many forms of life. Recently it was discovered that this ozone layer was getting depleted. Various man-made compounds like $CFCs$ (carbon compounds having both fluorine and chlorine which are very stable and not degraded by any biological process) were found to persist in the atmosphere. Once they reached the ozone layer, they would react with the ozone molecules. This resulted in a reduction of the ozone layer and recently they have discovered a hole in the ozone layer above the Antarctica. It is difficult to imagine the consequences for life on Earth if the ozone layer dwindles further, but many people think that it would be better not to take chances. These people advocate working towards stopping all further damage to the ozone layer.
(1) Identify the correct statement
Statement $1$ – Ozone is poisonous.
Statement $2$ – Absorbs harmful radiations from the Sun
Statement $3$ – Ozone prevents those harmful radiations from reaching the surface of the Earth.
Statement $4$ – Molecule containing three atoms of oxygen is termed as ozone.
$(a)$ Both $1$ & $4$
$(b)$ Both $2$ & $4$
$(c)$ Only $3$
$(d)$ All of the above
(2) The molecule containing three atoms of oxygen is termed as
$(a)$ Oxygen
$(b)$ Ozone
$(c)$ Diatomic oxygen
$(d)$ None of above
(3) What is the molecular formula of ozone?
$(a) O$
$(b )O2$
$(c) O3$
$(d) O4$
(4)Why ozone layer is important?
(5) What is CFC?
The fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur. When these fuels are burnt, nitrogen and sulphur too are burnt and this produces different oxides of nitrogen and sulphur. Not only is the inhalation of these gases dangerous, they also dissolve in rain to give rise to acid rain. The combustion of fossil fuels also increases the amount of suspended particles in air. These suspended particles could be unburnt carbon particles or substances called hydrocarbons. Presence of high levels of all these pollutants cause visibility to be lowered, especially in cold weather when water also condenses out of air. This is known as smog and is a visible indication of air pollution. Studies have shown that regularly breathing air that contains any of these substances increases the incidence of allergies, cancer and heart diseases. An increase in the content of these harmful substances in air is called air pollution.
(1) Identify the correct statement
Statement $1$ – The unburnt carbon particles which suspended in air called hydrocarbons.
Statement $2$ – Fossil fuels like coal and petroleum contain small amounts of nitrogen and sulphur.
Statement $3$ – In cold weather when water condenses out of air. This is known as smog.
Statement $4$ – Smog is the indication of air pollution
$(a)$ Both $1$ & $4$
$(b)$ Both $2$ & $4$
$(c)$ Only $3$
$(d)$ All of the above
(2) The unburnt carbon particles or substances which suspended in air are termed as ____
$(a)$ Smog
$(b)$ Fog
$(c)$ Hydrocarbons
$(d)$ Ozone
(3) An increase in the content of harmful substances in air is called as _________
$(a)$ Pollution
$(b)$ Air pollution
$(c)$ Smog
$(d)$ All of the above
(4)What is hydrocarbons?
(5) Enlist the adverse effect of air pollution on health.
‘scientific’ name for organisms in the same manner that chemical symbols and formulae for various substances are used in the world. The scientific name for an organism is thus unique and can be used to identify it anywhere in the world.The system of scientific naming or nomenclature we use today was introduced by Carolus Linnaeus in the eighteenth century. The scientific name of an organism isthe process of classification which puts it along with the organisms it is most related to. But when we actually name the species, we do not list out the whole hierarchy of groups it belongs to. Instead, we limit ourselves to writing the name of the genus and species of that particular organism. World over, it has been agreed that both these names will be used in Latin forms.
Certain conventions are followed while writing the scientific names:
(1) The name of the genus begins with a capital letter.
(2) The name of the species begins with a small letter.
(3) When printed, the scientific name is given in italics.
(4) When written by hand, the genus name and the species name have to be underlined separately.
(1) The system of scientific naming or nomenclature we use today was introduced by
$(a)$ Carolus Linnaeus
$(b)$ Ernst Haeckel
$(c)$ Robert Whittaker
$(d)$ Carl Woese
(2) When scientific name is printed is given in
$(a)$ Bold
$(b)$ Italics
$(c)$ Italic in lowercase
$(d)$ Bold in uppercase
(3) Identify the correct statement
Statement $1$ – Name of the genus begins with a capital letter.
Statement $2$ – Name of the species begins with a small letter.
Statement $3$ –Name of the genus begins with a small letter
Statement $4$ –When printed, the scientific name is given in bold
$(a)$ Both $1$ & $3$
$(b)$ Both $3$ & $4$
$(c)$ Both $1$ & $2$
$(d)$ All of the above
(4) Why is there a need for systematic naming of living organisms?
(5) Which rules and conventions are need to be followed while writing the scientific names?
A solution of a solid in a liquid such as water can be prepared by adding it slowly to water with constant stirring at a certain temperature (room temperature). If the addition process is continued, a stage is ultimately reached in the dissolution process when no more of the solid dissolves. Rather it starts setlling at the bottom of the container such as a glass beaker. The solution at this stage is said to be saturated. The solubility of a solute is always expressed with respect to the saturated solution. It may be defined as the maximum amount of the solute that can be dissolved in 100 g of the solvent to form a saturated solution at a given temperature. Please remember that the role of temperature is very important. If temperature is increased, the solution becomes unsaturated. In case the temperature is decreased, the solution becomes supersaturated. As a result, crust of the solute gets deposited on the surface.
i. What do mean by the term Solubility?
ii. 20 g of a solute are dissolved in 500 g of the solvent. The solubility of the solute is:
iii. When a saturated solution becomes unsaturated?
OR
What do you mean by concentration of solution?