CBSE > Class 09 > Science | CBSE Board | Homework Help

(i) It makes the systematic study of wide variety of organisms easier.
(ii) It gives interrelationship amongest different group of organisms.
(iii) It gives an idea about existing life forms on earth.

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When a solid melts, íts temperature remains the same, so where does the heat energy go?

Posted by Akki Aggarwal 7 years, 1 month ago

CBSE > Class 09 > Science

3 answers

Anchal Mishra 7 years, 1 month ago

The temperature is used to state chage

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Nikhil Kumar 7 years, 1 month ago

The heat ? energy is used to overcome the forces of attractions between the particles of matter.

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Pulkit Kumar 7 years, 1 month ago

This heat is used for changing solid into liquid state

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Archimedics principle

Posted by Arushi Shukla 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 1 month ago

When a body is immersed fully or partially in a fluid, it experiences an upward force that is equal to the weight of the fluid displaced by it.
If the weight of the water displaced is less than the weight of the object, the object will sink.
Archimedes’ principle has many applications :-

It is used in designing ships and submarines.
Lactometers, which are used to determine the purity of a sample of milk
Hydrometers used for determining density

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a skier of mass 50 kg stands at a top of a ski jump .He takes off from the top of h 75m calculate PE

Posted by Jayesh Ratlani 7 years, 1 month ago

CBSE > Class 09 > Science

3 answers

Raj Patel 7 years, 1 month ago

Mgh 75*50*10=37500

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Sk Kumar 7 years, 1 month ago

262500j

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Ronak Kanodia 7 years, 1 month ago

P.E if g=9.8 36750j ( mgh)

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Can u name the two organelles we have studied that contain their own genetic material

Posted by Karanpreet Singh 7 years, 1 month ago

CBSE > Class 09 > Science

2 answers

Raj Patel 7 years, 1 month ago

Mitochondria and plastids

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Karanpreet Singh 7 years, 1 month ago

Mitochondria and chloroplast are the two organelles that contain therir own genetic material

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Which postulate of dalton's atomic theory forms the basis of the law of conservation of mass

Posted by Gorang Dubey 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 1 month ago

The postulate of Dalton's atomic theory which says that " Atoms can neither be created nor destroyed in chemical reactions" is the result of the law of conservation of mass. Atoms are indivisible and indestructible. Atoms cannot be created nor destroyed in a chemical reaction.

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What is the colour of the skin cells

Posted by Tejas Kakde 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Shruti Priya 7 years, 1 month ago

The actual skin color of different humans is affected by many substances, although the single most important substance is the pigment melanin. Melanin is produced within the skin in cells called melanocytes and it is the main determinant of the skin color of darker-skinned humans

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The least count of a spring balance is 1gwt . When it suspended freely , the pointer is just in front of 2nd small division on the scale . Find the zero error

Posted by Sumona Banerjee 7 years, 1 month ago

CBSE > Class 09 > Science

0 answers

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How to complete syllabus in few Day of exam

Posted by Thapki❤️ Thapki❤️ 7 years, 1 month ago

CBSE > Class 09 > Science

0 answers

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Difine power

Posted by Rinku Singh 7 years, 1 month ago

CBSE > Class 09 > Science

3 answers

Prachi Janwani 7 years, 1 month ago

The rate of doing work is known as power. Power= work done /time.

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Simarpreet Singh 7 years, 1 month ago

Power is defined as the rate of doing work Power S.I unit is joule

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Isha Kumari 7 years, 1 month ago

Power is defined as the rate of doing work. Power=workdone/time

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State the difference between the cell wall of plant and fungi

Posted by Yucti Kumar 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Yogita Ingle 7 years, 1 month ago

One of the main differences between plants and fungi is that fungi have chitin as a component of their cell walls instead of cellulose. Both chitin and cellulose are comprised of polysaccharide chains.

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What is tha SONAR

Posted by Khan Khan 7 years, 1 month ago

CBSE > Class 09 > Science

2 answers

Gaurav Seth 7 years, 1 month ago

SONAR- The acronym SONAR stands for Sound Navigation and Ranging.

Sonar is a device that uses ultrasonic waves to measure the distance, direction and speed of underwater objects.

Principle: It uses the phenomenon of echoes in determining the sea-depth and locating the presence of under-water objects.

Working:

i) A strong beam of ultrasonic waves is sent from a transmitter mounted on the ship.

ii) The beam is reflected from the seabed and is received by an under-water detector which is also mounted on the ship.

iii) The time interval between transmission and reception of the ultrasonic signal is noted

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Khan Khan 7 years, 1 month ago

SONAR stand for sound navigation and herings

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Theory of glass slab

Posted by Gurvinder Singh 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Gaurav Seth 7 years, 1 month ago

Refraction through rectangular glass slab with parallel faces:
The refraction takes place at both air-glass interface and glass-air interface has the following characteristics:
- When a light ray travels from air to glass, the angle of incidence is greater than angle of refraction as ray bends towards normal.
- When a light ray travels from glass to air, the angle of refraction (also called angle of emergent in case of glass) is greater than the angle of incidence of glass-air interface as ray of light bends away from the normal.
- If the angle of incidence is zero, i.e. the incident ray is normal to the interface, the ray of light continues to travel in the same direction after refraction.
- The angle of emergence and angle of incidence will be equal.
  Emergent ray is parallel to the incident ray along with original direction but it will be laterally displaced to the left of the incident ray.
- For the same angle of incidence, lateral displacement is proportional to the thickness of the glass slab.
- For the same thickness of glass slab, the lateral displacement is proportional to the angle of incidence.

AIM
To trace the path of a ray of light passing through a rectangular glass slab for different angles of incidence. Measure the angle of incidence, angle of refraction, angle of emergence and interpret the result.

MATERIALS REQUIRED
Drawing board, drawing pins, three plane sheets of white paper, a rectangular glass slab, geometry instruments, and sharp pointed pins.

THEORY
The refraction takes place at both air-glass interface and glass-air interface of a rectangular glass slab.

When the light ray incident on air-glass interface (DC) obliquely, it bends towards the normal.
The refracted ray is incident obliquely on the second parallel surface inside the rectangular glass slab, i. e. glass-air interface (AB) and after refraction, it moves away from the normal.
These refractions at both the surfaces obey the laws of refraction (Refer to basic building concept).

PROCEDURE

Fix a white paper on a drawing board with the help of drawing pins and divide the sheet in two parts by a vertical line.
Place a rectangular glass slab in the first part. Draw its boundary. Remove the glass slab and label the boundary as A₁, B₁, C₁, D₁ as shown below.
Draw a normal (perpendicular) MN on the side A₁B₁ at a point O₁, slightly away from the centre towards A₁
Draw an oblique line P₁Q₁ (incident ray) such that ∠P₁O₁M = 30° (Angle of incidence). Fix two sharp pointed pin P₁ and Q₁ vertically erected on the line P₁O₁ at a distance of 4 to 6 cm apart.
Place the glass slab again within its boundary. Look at the feet of pins (not their heads) P₁ and Q₁from the other parallel opposite face of the slab, i.e. from C₁D₁ along the plane of paper. Fix other two pins R₁ and S₁ in such a way that R₁ , S₁ and the image of P₁ and Q₁ lie on a same straight line.
Remove the glass slab and all the four pins. Encircle all the prick of the four pins. Join the points R₁and S₁ within the encircle and produce upto the edge C₁D₁. Let R₁S₁ meet C₁D₁ at O₁. This will act as an emergent ray.
Draw a normal M₁N₁ at O₂. Join O₁ and O₂. It will represent the path of ray inside the glass slab, i.e. refracted ray.
Measure the angle of emergence, i.e. ∠e = ∠N₁O₁S₁ and angle of refraction, i.e. ∠r = ∠NO₁O₂
Repeat the experiment by taking the different angles of incidence such as 45° and 60° on the other part of paper and measure the angle of refraction and emergence accordingly and tabulate them.

OBSERVATION TABLE

RESULT

At the point of incidence the incident ray, refracted ray and the normal to the air-glass interface, all lie in the plane of paper.
Within experimental limits, the angle of emergence and angle of incidence are equal.
The emergent ray is parallel to the incident ray.
Emergent ray is laterally displaced.
When the light ray travels from optically rarer medium (air) to optically denser medium (glass), the angle of refraction is less than the angle of incidence.
The refracted angle at the air-glass interface and the incident angle at the glass-air interface are found to be equal.
From the observation table, it is clear that with the increase in angle of incidence, angle of refraction also increases.

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Differentiate between squamous, cuboidal and elongated epithelial tissue

Posted by Pushp Sharma 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Meghna Thapar 6 years, 1 month ago

Squamous

Cuboidal

Columnar

i. It is made up of thin, flat and irregular-shaped cells. It forms the delicate lining of cavities (mouth, oesophagus, nose, etc.) and blood vessels.

ii. It protects the underlying parts of body from mechanical injury, entry of germs, chemicals and drying.

i. It consists of cube-like cells. These are found in kidney tubules, thyroid vesicles and in glands.

ii. It helps in absorption, secretion and excretion. It also provides mechanical support.

i. It consists of cells which are taller than broader i.e. pillar-like. It forms the lining of stomach, small intestine and colon.

ii. Its main function includes absorption and secretion.

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What is the effect of pressure on boiling point

Posted by Honey Sharma 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Vikash Kumar 7 years, 1 month ago

As Pressure increases,the boiling point of substances increases.

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D/b chordata and non chordet

Posted by Ramdas Yadav 7 years, 1 month ago

CBSE > Class 09 > Science

1 answers

Meghna Thapar 6 years, 1 month ago

Chordates are characterised by the following three features: (a) a dorsal, hollow, tubular nerve cord; (b) a pliable rod called notochord that occurs ventral to nerve cord and is replaced by a bone or cartilage to form a vertebral column in vertebrates; and (c) paired gill-slits in the pharynx. However, non-chordates are animals without a notochord – the rod-like elastic structure that supports the body. This phylum consists of a small group of worm-like, marine species with an organ-system level of organization.

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What is diffusion.explain with an example.

Posted by Gokul P 7 years, 1 month ago

CBSE > Class 09 > Science

4 answers

Raj Patel 7 years, 1 month ago

Diffusion is a process of movement of gases from an area of heigher concentration to an area of lower concentration through a medium Eg. Movement of gases inside cell

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Isha Kumari 7 years, 1 month ago

Diffusion is the intermixing of particles of two different types of matter on their own . Example-the smell of incense stick ,the smell of perfume,etc

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Lakhwinder Singh Dhalli 7 years, 1 month ago

sprading of gases

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Harshit Kumar Deo 7 years, 1 month ago

The smell iscense(agarbatti) mix in air then we say that it is sm

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A car accelerates at a m/s² for some time after which it decelerates at 2a m/s² , to come to rest. If the time taken is t s then evaluate the total distance travelled.( Solve mathematically )

Posted by Swattik Mukhopadhyay 7 years, 1 month ago

CBSE > Class 09 > Science