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Science Class 9

Created by: Dr Manju Sen

Class 9 : Notes | EduRev

 Page 1


  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
CBSE  
Class IX Science 
Sample Paper – 2 Solution  
 
Section A 
1. Pseudomonas 
 
2. Fumigation is the most effective method for destroying insects in stored grains. 
 
Section B 
3. Factors which affect the value of g: (any two)  
(i) Shape of the Earth: The Earth is not perfectly spherical. It is slightly flattened at the 
poles and bulgy towards the equator. The value of g is maximum (9.83 m/s
2
) at the 
poles as the polar radius is minimum, while it is minimum (9.78 m/s
2
) at the 
equator as the equatorial radius is maximum. 
(ii)  Altitude: As the height (h) above the Earth’s surface increases, the value of g 
decreases. It varies by a value of
?
2
1
(R h)
, where R is the radius of the Earth. 
(iii) Depth: In the interior of the Earth, on an average, the value of g is less than that at 
the Earth’s surface. As the depth below the Earth’s surface increases, the value of g 
decreases, and finally, it becomes zero at the centre of the Earth. 
OR 
(i) Mass is the amount of matter contained in a body. So, it can never be zero.  
(ii) Weight is the force with which the body is attracted towards the centre of the Earth. 
(iii) Mathematically, weight is the product of mass (m) and acceleration due to gravity 
(g). At the centre of the Earth, g is zero.  
(iv) Hence, weight is zero. This shows that a body can have mass but no weight. 
4.  
Cathode rays Anode rays 
These rays travel from the cathode to the 
anode. 
These rays travel from the anode to the 
cathode. 
They are made of negatively charged 
particles. 
They are made of positively charged 
particles. 
They produce a greenish yellow 
fluorescence on a soda-glass screen. 
They produce fluorescence on a zinc 
sulphide screen. 
They are affected by an electric field, i.e. 
they are inflected towards a positive 
field and deflected towards a negative 
field. 
They are deflected by electric and 
magnetic fields but in a direction 
opposite to that of cathode rays. 
Page 2


  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
CBSE  
Class IX Science 
Sample Paper – 2 Solution  
 
Section A 
1. Pseudomonas 
 
2. Fumigation is the most effective method for destroying insects in stored grains. 
 
Section B 
3. Factors which affect the value of g: (any two)  
(i) Shape of the Earth: The Earth is not perfectly spherical. It is slightly flattened at the 
poles and bulgy towards the equator. The value of g is maximum (9.83 m/s
2
) at the 
poles as the polar radius is minimum, while it is minimum (9.78 m/s
2
) at the 
equator as the equatorial radius is maximum. 
(ii)  Altitude: As the height (h) above the Earth’s surface increases, the value of g 
decreases. It varies by a value of
?
2
1
(R h)
, where R is the radius of the Earth. 
(iii) Depth: In the interior of the Earth, on an average, the value of g is less than that at 
the Earth’s surface. As the depth below the Earth’s surface increases, the value of g 
decreases, and finally, it becomes zero at the centre of the Earth. 
OR 
(i) Mass is the amount of matter contained in a body. So, it can never be zero.  
(ii) Weight is the force with which the body is attracted towards the centre of the Earth. 
(iii) Mathematically, weight is the product of mass (m) and acceleration due to gravity 
(g). At the centre of the Earth, g is zero.  
(iv) Hence, weight is zero. This shows that a body can have mass but no weight. 
4.  
Cathode rays Anode rays 
These rays travel from the cathode to the 
anode. 
These rays travel from the anode to the 
cathode. 
They are made of negatively charged 
particles. 
They are made of positively charged 
particles. 
They produce a greenish yellow 
fluorescence on a soda-glass screen. 
They produce fluorescence on a zinc 
sulphide screen. 
They are affected by an electric field, i.e. 
they are inflected towards a positive 
field and deflected towards a negative 
field. 
They are deflected by electric and 
magnetic fields but in a direction 
opposite to that of cathode rays. 
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
5.  
(a) Pear consists of sclereids or stone cells.  
(b) They form the gritty part of most ripe fruits and contribute hardness to the seed 
coat and nutshell. 
(c) Therefore, when we chew a pear, we get a crunchy and granular feeling due to the 
presence of sclereids. 
 
Section C 
 
6.  
(a) Ribosome 
(b) Leucoplast 
(c) Nucleolus  
 
7.  
(a) Arthropoda: Jointed legs or appendages 
(b) Annelida: Metamerically segmented body 
(c) Porifera: Body perforated with numerous pores 
OR 
Differences between amphibians and reptiles: 
Amphibians Reptiles 
1. Skin is glandular, smooth and 
moist. 
1. Skin is non-glandular, dry and 
keratinised. 
2. Have a three-chambered heart. 2. Have an incomplete four-
chambered heart. 
3. Fertilisation is external. 3. Fertilisation is internal. 
4. Examples: Frog, toad 4. Examples: Snake, lizard 
 
 
8.  
(i) Net force F = F2 ? F1 = 30 ? 20 = 10 N 
(ii) Net force acts along the direction of F2. 
(iii) Acceleration F = ma 
?
? ? ?
2
10
a 1 ms
10
 
 
9. There are colloidal particles of mist in the forest.  
When light passes through the canopy of the forest, these colloidal particles are 
scattered and we observe the Tyndall effect.  
Smoke and milk also show the Tyndall effect. 
 
  
Page 3


  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
CBSE  
Class IX Science 
Sample Paper – 2 Solution  
 
Section A 
1. Pseudomonas 
 
2. Fumigation is the most effective method for destroying insects in stored grains. 
 
Section B 
3. Factors which affect the value of g: (any two)  
(i) Shape of the Earth: The Earth is not perfectly spherical. It is slightly flattened at the 
poles and bulgy towards the equator. The value of g is maximum (9.83 m/s
2
) at the 
poles as the polar radius is minimum, while it is minimum (9.78 m/s
2
) at the 
equator as the equatorial radius is maximum. 
(ii)  Altitude: As the height (h) above the Earth’s surface increases, the value of g 
decreases. It varies by a value of
?
2
1
(R h)
, where R is the radius of the Earth. 
(iii) Depth: In the interior of the Earth, on an average, the value of g is less than that at 
the Earth’s surface. As the depth below the Earth’s surface increases, the value of g 
decreases, and finally, it becomes zero at the centre of the Earth. 
OR 
(i) Mass is the amount of matter contained in a body. So, it can never be zero.  
(ii) Weight is the force with which the body is attracted towards the centre of the Earth. 
(iii) Mathematically, weight is the product of mass (m) and acceleration due to gravity 
(g). At the centre of the Earth, g is zero.  
(iv) Hence, weight is zero. This shows that a body can have mass but no weight. 
4.  
Cathode rays Anode rays 
These rays travel from the cathode to the 
anode. 
These rays travel from the anode to the 
cathode. 
They are made of negatively charged 
particles. 
They are made of positively charged 
particles. 
They produce a greenish yellow 
fluorescence on a soda-glass screen. 
They produce fluorescence on a zinc 
sulphide screen. 
They are affected by an electric field, i.e. 
they are inflected towards a positive 
field and deflected towards a negative 
field. 
They are deflected by electric and 
magnetic fields but in a direction 
opposite to that of cathode rays. 
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
5.  
(a) Pear consists of sclereids or stone cells.  
(b) They form the gritty part of most ripe fruits and contribute hardness to the seed 
coat and nutshell. 
(c) Therefore, when we chew a pear, we get a crunchy and granular feeling due to the 
presence of sclereids. 
 
Section C 
 
6.  
(a) Ribosome 
(b) Leucoplast 
(c) Nucleolus  
 
7.  
(a) Arthropoda: Jointed legs or appendages 
(b) Annelida: Metamerically segmented body 
(c) Porifera: Body perforated with numerous pores 
OR 
Differences between amphibians and reptiles: 
Amphibians Reptiles 
1. Skin is glandular, smooth and 
moist. 
1. Skin is non-glandular, dry and 
keratinised. 
2. Have a three-chambered heart. 2. Have an incomplete four-
chambered heart. 
3. Fertilisation is external. 3. Fertilisation is internal. 
4. Examples: Frog, toad 4. Examples: Snake, lizard 
 
 
8.  
(i) Net force F = F2 ? F1 = 30 ? 20 = 10 N 
(ii) Net force acts along the direction of F2. 
(iii) Acceleration F = ma 
?
? ? ?
2
10
a 1 ms
10
 
 
9. There are colloidal particles of mist in the forest.  
When light passes through the canopy of the forest, these colloidal particles are 
scattered and we observe the Tyndall effect.  
Smoke and milk also show the Tyndall effect. 
 
  
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
10. Advantages of mixed cropping: 
(a) Risk of total crop failure because of an uncertain monsoon is reduced. 
(b) Yield of crops is increased because of the complementary effect of component crops. 
(c) Soil fertility is improved by growing two crops simultaneously. 
(d) Chances of pest infection are greatly reduced. 
Disadvantages of mixed cropping: 
(a) There is a difficulty in fertiliser application and spraying of pesticides to individual 
crops. 
(b) Separate harvesting and threshing of crops is not possible. 
(c) Marketing and consumption of only mixed produce are possible.  
 
11.  
(a) Whales and fish are aquatic animals and belong to Phylum Chordata. However, they 
both differ in several basic characters. 
(b) Whales are warm-blooded, while fish are cold-blooded animals. 
(c) Whales respire through the lungs, while fish breathe through gills. 
(d) Whales possess mammary glands which are absent in fish. 
(e) Whales have a four-chambered heart, while fish have a two-chambered heart. 
(f) Therefore, although both resemble each other and swim in water, whales cannot be 
grouped with fish.  
(g) Whales belong to Class Mammalia, whiles fish are included in Class Pisces. 
 
12. 1 mole of Ca = 40 g  
No. of atoms of calcium = no. of moles × 6.022 × 10
23
 
= (Given Mass/Molar Mass) × 6.022 × 10
23
 
                                               = (125/40) × 6.022 × 10
23
 
                                               = 1.88 × 10
24
 atoms  
No. of atoms of iron = (Given Mass/Molar Mass) × 6.022 × 10
23
 
= (130/56) × 6.022 × 10
23
 
= 1.39 × 10
24
 atoms  
Calcium has more number of atoms.  
Difference in number of atoms = 1.88 × 10
24
- 1.39 × 10
24
 
     = 10
24
 (1.88 - 1.39)  
            = 0.49 × 10
24 
               = 4.9 × 10
23
 atoms 
OR 
Mass of sodium carbonate + mass of ethanoic acid = mass of sodium ethanoate + mass 
of water + mass of carbon dioxide  
5.6 g + 7.0 g = x + 2.8 + 0.7 g  
x = 12.6 - 3.5 = 9.1 g 
 
  
Page 4


  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
CBSE  
Class IX Science 
Sample Paper – 2 Solution  
 
Section A 
1. Pseudomonas 
 
2. Fumigation is the most effective method for destroying insects in stored grains. 
 
Section B 
3. Factors which affect the value of g: (any two)  
(i) Shape of the Earth: The Earth is not perfectly spherical. It is slightly flattened at the 
poles and bulgy towards the equator. The value of g is maximum (9.83 m/s
2
) at the 
poles as the polar radius is minimum, while it is minimum (9.78 m/s
2
) at the 
equator as the equatorial radius is maximum. 
(ii)  Altitude: As the height (h) above the Earth’s surface increases, the value of g 
decreases. It varies by a value of
?
2
1
(R h)
, where R is the radius of the Earth. 
(iii) Depth: In the interior of the Earth, on an average, the value of g is less than that at 
the Earth’s surface. As the depth below the Earth’s surface increases, the value of g 
decreases, and finally, it becomes zero at the centre of the Earth. 
OR 
(i) Mass is the amount of matter contained in a body. So, it can never be zero.  
(ii) Weight is the force with which the body is attracted towards the centre of the Earth. 
(iii) Mathematically, weight is the product of mass (m) and acceleration due to gravity 
(g). At the centre of the Earth, g is zero.  
(iv) Hence, weight is zero. This shows that a body can have mass but no weight. 
4.  
Cathode rays Anode rays 
These rays travel from the cathode to the 
anode. 
These rays travel from the anode to the 
cathode. 
They are made of negatively charged 
particles. 
They are made of positively charged 
particles. 
They produce a greenish yellow 
fluorescence on a soda-glass screen. 
They produce fluorescence on a zinc 
sulphide screen. 
They are affected by an electric field, i.e. 
they are inflected towards a positive 
field and deflected towards a negative 
field. 
They are deflected by electric and 
magnetic fields but in a direction 
opposite to that of cathode rays. 
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
5.  
(a) Pear consists of sclereids or stone cells.  
(b) They form the gritty part of most ripe fruits and contribute hardness to the seed 
coat and nutshell. 
(c) Therefore, when we chew a pear, we get a crunchy and granular feeling due to the 
presence of sclereids. 
 
Section C 
 
6.  
(a) Ribosome 
(b) Leucoplast 
(c) Nucleolus  
 
7.  
(a) Arthropoda: Jointed legs or appendages 
(b) Annelida: Metamerically segmented body 
(c) Porifera: Body perforated with numerous pores 
OR 
Differences between amphibians and reptiles: 
Amphibians Reptiles 
1. Skin is glandular, smooth and 
moist. 
1. Skin is non-glandular, dry and 
keratinised. 
2. Have a three-chambered heart. 2. Have an incomplete four-
chambered heart. 
3. Fertilisation is external. 3. Fertilisation is internal. 
4. Examples: Frog, toad 4. Examples: Snake, lizard 
 
 
8.  
(i) Net force F = F2 ? F1 = 30 ? 20 = 10 N 
(ii) Net force acts along the direction of F2. 
(iii) Acceleration F = ma 
?
? ? ?
2
10
a 1 ms
10
 
 
9. There are colloidal particles of mist in the forest.  
When light passes through the canopy of the forest, these colloidal particles are 
scattered and we observe the Tyndall effect.  
Smoke and milk also show the Tyndall effect. 
 
  
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
10. Advantages of mixed cropping: 
(a) Risk of total crop failure because of an uncertain monsoon is reduced. 
(b) Yield of crops is increased because of the complementary effect of component crops. 
(c) Soil fertility is improved by growing two crops simultaneously. 
(d) Chances of pest infection are greatly reduced. 
Disadvantages of mixed cropping: 
(a) There is a difficulty in fertiliser application and spraying of pesticides to individual 
crops. 
(b) Separate harvesting and threshing of crops is not possible. 
(c) Marketing and consumption of only mixed produce are possible.  
 
11.  
(a) Whales and fish are aquatic animals and belong to Phylum Chordata. However, they 
both differ in several basic characters. 
(b) Whales are warm-blooded, while fish are cold-blooded animals. 
(c) Whales respire through the lungs, while fish breathe through gills. 
(d) Whales possess mammary glands which are absent in fish. 
(e) Whales have a four-chambered heart, while fish have a two-chambered heart. 
(f) Therefore, although both resemble each other and swim in water, whales cannot be 
grouped with fish.  
(g) Whales belong to Class Mammalia, whiles fish are included in Class Pisces. 
 
12. 1 mole of Ca = 40 g  
No. of atoms of calcium = no. of moles × 6.022 × 10
23
 
= (Given Mass/Molar Mass) × 6.022 × 10
23
 
                                               = (125/40) × 6.022 × 10
23
 
                                               = 1.88 × 10
24
 atoms  
No. of atoms of iron = (Given Mass/Molar Mass) × 6.022 × 10
23
 
= (130/56) × 6.022 × 10
23
 
= 1.39 × 10
24
 atoms  
Calcium has more number of atoms.  
Difference in number of atoms = 1.88 × 10
24
- 1.39 × 10
24
 
     = 10
24
 (1.88 - 1.39)  
            = 0.49 × 10
24 
               = 4.9 × 10
23
 atoms 
OR 
Mass of sodium carbonate + mass of ethanoic acid = mass of sodium ethanoate + mass 
of water + mass of carbon dioxide  
5.6 g + 7.0 g = x + 2.8 + 0.7 g  
x = 12.6 - 3.5 = 9.1 g 
 
  
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
13.  
(i) The boat floats lower in water, that is, it sinks a little more in water. 
(ii) Weight of water displaced by the submerged part of the boat increases. 
(iii) Because of the greater weight of water displaced, the buoyant force acting on the 
boat increases. This greater buoyant force enables the extra weight of the man in the 
boat.  
 
14.  
(a) The centrifugation technique is used in the process.  
(b) The same technique is used to extract cream from milk.  
(c) Rohini’s mother teaches us the value of saving water. 
 
15. Table A 
 
Height from 
which an 
object is 
dropped 
‘h’ (m) 
Velocity of an 
object falling 
from the 
height 
‘v
2
’ (m/s
2
) 
Potential 
energy 
mgh (J) 
Kinetic 
energy 
½mv
2
 (J) 
TE =  
PE + KE 
10 0 20 ? 10 ?10  
= 2000 
½ ? 20 ? 0 = 0  2000 
2 80 20 ? 10 ?2  
= 400 
½ ? 20 ? 80 = 
800  
1200 
 
Table B 
Height from 
which an 
object is 
dropped 
‘h’ (m) 
Velocity of an 
object falling 
from the 
height 
‘v
2
’ (m/s
2
) 
Potential 
energy 
mgh (J) 
Kinetic 
energy 
½mv
2
 (J) 
TE =  
PE + KE 
10 0 20 ? 10 ?10  
= 2000 
½ ? 20 ? 0 = 0  2000 
2 40 20 ? 10 ?2  
= 400 
½ ? 20 ? 40 = 
400  
800 
 
According to the law of conservation of energy, the sum of potential energy and 
kinetic energy of the object should remain the same at every point during its fall. 
OR 
  
Page 5


  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
CBSE  
Class IX Science 
Sample Paper – 2 Solution  
 
Section A 
1. Pseudomonas 
 
2. Fumigation is the most effective method for destroying insects in stored grains. 
 
Section B 
3. Factors which affect the value of g: (any two)  
(i) Shape of the Earth: The Earth is not perfectly spherical. It is slightly flattened at the 
poles and bulgy towards the equator. The value of g is maximum (9.83 m/s
2
) at the 
poles as the polar radius is minimum, while it is minimum (9.78 m/s
2
) at the 
equator as the equatorial radius is maximum. 
(ii)  Altitude: As the height (h) above the Earth’s surface increases, the value of g 
decreases. It varies by a value of
?
2
1
(R h)
, where R is the radius of the Earth. 
(iii) Depth: In the interior of the Earth, on an average, the value of g is less than that at 
the Earth’s surface. As the depth below the Earth’s surface increases, the value of g 
decreases, and finally, it becomes zero at the centre of the Earth. 
OR 
(i) Mass is the amount of matter contained in a body. So, it can never be zero.  
(ii) Weight is the force with which the body is attracted towards the centre of the Earth. 
(iii) Mathematically, weight is the product of mass (m) and acceleration due to gravity 
(g). At the centre of the Earth, g is zero.  
(iv) Hence, weight is zero. This shows that a body can have mass but no weight. 
4.  
Cathode rays Anode rays 
These rays travel from the cathode to the 
anode. 
These rays travel from the anode to the 
cathode. 
They are made of negatively charged 
particles. 
They are made of positively charged 
particles. 
They produce a greenish yellow 
fluorescence on a soda-glass screen. 
They produce fluorescence on a zinc 
sulphide screen. 
They are affected by an electric field, i.e. 
they are inflected towards a positive 
field and deflected towards a negative 
field. 
They are deflected by electric and 
magnetic fields but in a direction 
opposite to that of cathode rays. 
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
5.  
(a) Pear consists of sclereids or stone cells.  
(b) They form the gritty part of most ripe fruits and contribute hardness to the seed 
coat and nutshell. 
(c) Therefore, when we chew a pear, we get a crunchy and granular feeling due to the 
presence of sclereids. 
 
Section C 
 
6.  
(a) Ribosome 
(b) Leucoplast 
(c) Nucleolus  
 
7.  
(a) Arthropoda: Jointed legs or appendages 
(b) Annelida: Metamerically segmented body 
(c) Porifera: Body perforated with numerous pores 
OR 
Differences between amphibians and reptiles: 
Amphibians Reptiles 
1. Skin is glandular, smooth and 
moist. 
1. Skin is non-glandular, dry and 
keratinised. 
2. Have a three-chambered heart. 2. Have an incomplete four-
chambered heart. 
3. Fertilisation is external. 3. Fertilisation is internal. 
4. Examples: Frog, toad 4. Examples: Snake, lizard 
 
 
8.  
(i) Net force F = F2 ? F1 = 30 ? 20 = 10 N 
(ii) Net force acts along the direction of F2. 
(iii) Acceleration F = ma 
?
? ? ?
2
10
a 1 ms
10
 
 
9. There are colloidal particles of mist in the forest.  
When light passes through the canopy of the forest, these colloidal particles are 
scattered and we observe the Tyndall effect.  
Smoke and milk also show the Tyndall effect. 
 
  
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
10. Advantages of mixed cropping: 
(a) Risk of total crop failure because of an uncertain monsoon is reduced. 
(b) Yield of crops is increased because of the complementary effect of component crops. 
(c) Soil fertility is improved by growing two crops simultaneously. 
(d) Chances of pest infection are greatly reduced. 
Disadvantages of mixed cropping: 
(a) There is a difficulty in fertiliser application and spraying of pesticides to individual 
crops. 
(b) Separate harvesting and threshing of crops is not possible. 
(c) Marketing and consumption of only mixed produce are possible.  
 
11.  
(a) Whales and fish are aquatic animals and belong to Phylum Chordata. However, they 
both differ in several basic characters. 
(b) Whales are warm-blooded, while fish are cold-blooded animals. 
(c) Whales respire through the lungs, while fish breathe through gills. 
(d) Whales possess mammary glands which are absent in fish. 
(e) Whales have a four-chambered heart, while fish have a two-chambered heart. 
(f) Therefore, although both resemble each other and swim in water, whales cannot be 
grouped with fish.  
(g) Whales belong to Class Mammalia, whiles fish are included in Class Pisces. 
 
12. 1 mole of Ca = 40 g  
No. of atoms of calcium = no. of moles × 6.022 × 10
23
 
= (Given Mass/Molar Mass) × 6.022 × 10
23
 
                                               = (125/40) × 6.022 × 10
23
 
                                               = 1.88 × 10
24
 atoms  
No. of atoms of iron = (Given Mass/Molar Mass) × 6.022 × 10
23
 
= (130/56) × 6.022 × 10
23
 
= 1.39 × 10
24
 atoms  
Calcium has more number of atoms.  
Difference in number of atoms = 1.88 × 10
24
- 1.39 × 10
24
 
     = 10
24
 (1.88 - 1.39)  
            = 0.49 × 10
24 
               = 4.9 × 10
23
 atoms 
OR 
Mass of sodium carbonate + mass of ethanoic acid = mass of sodium ethanoate + mass 
of water + mass of carbon dioxide  
5.6 g + 7.0 g = x + 2.8 + 0.7 g  
x = 12.6 - 3.5 = 9.1 g 
 
  
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
13.  
(i) The boat floats lower in water, that is, it sinks a little more in water. 
(ii) Weight of water displaced by the submerged part of the boat increases. 
(iii) Because of the greater weight of water displaced, the buoyant force acting on the 
boat increases. This greater buoyant force enables the extra weight of the man in the 
boat.  
 
14.  
(a) The centrifugation technique is used in the process.  
(b) The same technique is used to extract cream from milk.  
(c) Rohini’s mother teaches us the value of saving water. 
 
15. Table A 
 
Height from 
which an 
object is 
dropped 
‘h’ (m) 
Velocity of an 
object falling 
from the 
height 
‘v
2
’ (m/s
2
) 
Potential 
energy 
mgh (J) 
Kinetic 
energy 
½mv
2
 (J) 
TE =  
PE + KE 
10 0 20 ? 10 ?10  
= 2000 
½ ? 20 ? 0 = 0  2000 
2 80 20 ? 10 ?2  
= 400 
½ ? 20 ? 80 = 
800  
1200 
 
Table B 
Height from 
which an 
object is 
dropped 
‘h’ (m) 
Velocity of an 
object falling 
from the 
height 
‘v
2
’ (m/s
2
) 
Potential 
energy 
mgh (J) 
Kinetic 
energy 
½mv
2
 (J) 
TE =  
PE + KE 
10 0 20 ? 10 ?10  
= 2000 
½ ? 20 ? 0 = 0  2000 
2 40 20 ? 10 ?2  
= 400 
½ ? 20 ? 40 = 
400  
800 
 
According to the law of conservation of energy, the sum of potential energy and 
kinetic energy of the object should remain the same at every point during its fall. 
OR 
  
  
 
CBSE IX | SCIENCE 
Sample Paper – 2 Solution 
 
      
Time of ascent = Time of descent = 6/2 = 3 s 
(a) 
2
v 0,a g 9.8 m/s ? ? ? ? ? 
According to the first equation of motion, we have 
  
v u at
0 u 9.8 3
u 29.4 m/s
??
? ? ?
?
 
Hence, the ball was thrown up with a speed of 29.4 m/s. 
(b)  According to the second equation of motion, we have 
  
22
2
2
v u 2as
0 29.4 2 9.8 h
29.4
h 44.1 m
19.6
??
? ? ? ?
??
 
Hence, the ball reaches a maximum height of 44.1 m. 
 
(c)  After the first three seconds, the ball is moving downwards.  
Hence, 4 s after launch means 1 s after reaching the maximum height. 
Thus, according to the third equation of motion, we have 
  
2
2
1
s ut at
2
1
h 0 9.8 1
2
h 4.9 m
??
? ? ? ?
?
 
Hence, its position after 4 s is 44.1 – 4.9 = 39.2 m from the ground. 
 
Section D 
16.  
(a) Niels Bohr revised Rutherford’s atomic model and put forth the following 
suggestions: 
? Niels Bohr proposed that the electrons possess a specific amount of energy 
which allows them to revolve around the nucleus.  
? An atom contains discrete orbits which correspond to specific amount of energy. 
Hence, these orbits are also known as energy levels. 
? Energy levels of an atom are represented as K, L, M, N and so on or the numbers 
n = 1, 2, 3, 4 and so on. 
 
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