Lakhmir Singh Manjit Kaur Physics 2020 2021 for Class 9 Science Chapter 9 - Model Test Paper 3

Answer:

Platyhelminthes show organ level of organisation.

Answer:

Answer:

Components of phloem and their functions are as follows -

1. Sieve tube − Transport food materials
2. Companion cells − Carry out the cellular functions of the sieve tube elements
3. Phloem parenchyma − Responsible for the storage of food
4. Phloem fibres − Provide mechanical strength to the cells

The process of transport of food from the leaves to the other parts of a plant is known as translocation.

Answer:

(a) Distance travelled by the stone while falling from the height 20 m to the ground = 20 m

The initial velocity of the stone = 0

Acceleration of the stone = g

By using the second equation of  motion, we can write, $s=ut+\frac{1}{2}g{t}^2$

Here, u = 0, s = 20 m, and 't'  is the time taken by the stone to reach the ground.

So,

$$\begin{gathered} 20 =0 + \frac{1}{2}\times g\mathit{\times }{t}^{\mathit{2}} \\ \mathit{\Rightarrow }{t}^{\mathit{2}}=\frac{40}{\mathrm{g}}=\frac{40}{10}=4 \\ \mathit{\Rightarrow }t=4 \mathrm{s} \end{gathered}$$

(b) Using the first equation of motion, we can write, $v = u + gt$ (Where 'v' is the speed of the stone when it hits the ground)

So, $v = 0 + 10\times 4=40 \mathrm{m}/\mathrm{s}$



 

Answer:

In big halls or auditoriums, the sound is absorbed by the walls, ceilings, and seats, that's why a curved board is placed behind the speaker such that the speaker is at the focus point of the curved surface. The curved surface or the board used for this purpose is known as a soundboard.

Soundboard makes the sound of the speaker louder and clear because after multiple reflections of the sound at the curved surface all the reflected rays distribute uniformly to the audience and sound is heard more clearly. As you can see in the figure, the source is always placed at the focus of the curved surface, and curved board is placed behind the source of the sound so that the sound gets reflected from the soundboard and distributed uniformly to the front.

Answer:

(a) The sound waves bounced back after striking a hard surface are known as reflected rays and the phenomenon is known as the reflection of the sound. Sound is reflected well from hard surfaces like a wall, metal sheet or a hardwood. 

(b) Hard objects are the good reflectors of the sound, like steel and iron.

(c) There are two laws of reflections. 

(i) The incident ray, the normal and the reflected ray, all lie in the same plane.
(ii) The angle of incidence is always equal to the angle of reflection.

Answer:

Answer:

(a) The formula mass of sodium oxide,
$$\begin{gathered} \mathrm{Formula} \mathrm{mass} \mathrm{of} {\mathrm{Na}}_2\mathrm{O}= 2\times \mathrm{atomic} \mathrm{mass} \mathrm{of} \mathrm{Na}+\mathrm{atomic} \mathrm{mass} \mathrm{of} \mathrm{oxygen} \\ \mathrm{Formula} \mathrm{mass} \mathrm{of} {\mathrm{Na}}_2\mathrm{O}= 2\times 23+16 \\ \mathrm{Formula} \mathrm{mass} \mathrm{of} {\mathrm{Na}}_2\mathrm{O}= 62 \mathrm{u} \end{gathered}$$

(b) The formula mass of aluminum oxide,
$$\begin{gathered} \mathrm{Formula} \mathrm{mass} \mathrm{of} {\mathrm{Al}}_2{\mathrm{O}}_3= 2\times \mathrm{atomic} \mathrm{mass} \mathrm{of} \mathrm{Al}+3\times \mathrm{atomic} \mathrm{mass} \mathrm{of} \mathrm{oxygen} \\ \mathrm{Formula} \mathrm{mass} \mathrm{of} {\mathrm{Al}}_2{\mathrm{O}}_3= 2\times 27+3\times 16 \\ \mathrm{Formula} \mathrm{mass} \mathrm{of} {\mathrm{Al}}_2{\mathrm{O}}_3= 102 \mathrm{u} \end{gathered}$$

Answer:

The person is suffering from AIDS. It is a disease which affects the immune system and lowers the immunity of the suffering individual. As a result of which the person becomes susceptible to all types of infections.
HIV (Human immuno virus) is the causal organism. It belongs to the category of viruses.

AIDS can spread by any one of the following ways-

(i) through sexual contact with the infected person

(ii) from the mother to her child, through the placenta

(iii) transfusion of infected blood to healthy individual.

(iv) by the use of infected syringe

Answer:

(a) There are two forms of oxygen found in the atmosphere -

Elemental oxygen - It is usually found in diatomic state i.e. O₂ in the lower part of atmosphere.
Ozone - Another form of oxygen is ozone, which exists in triatomic state i.e. O₃ and is found in the stratosphere layer of atmosphere.

(b) Forests play an important role in various ways -

• They maintain the carbon dioxide and oxygen balance. They use carbon dioxide and release oxygen into the atmosphere.
• They play an important role in replenishing the water resources by maintaining the water cycle.
• They prevent soil erosion by strongly holding onto the soil through their roots and preventing it from eroding.
• They also check the speed of winds and running water.

Answer:

(a) The rate of change of displacement is known as the velocity. It can be calculated by obtaining the ratio of displacement and the total time taken. The SI unit of velocity is 'm/s', same as of the speed. 

(b) Speed is the rate of change of distance travelled by a body whereas velocity is the rate of change of displacement by the body. Speed is a directionless quantity but the velocity is a vector quantity, we need magnitude as well as direction to describe it. 

(c) Given speed, v = 54 km/h

1 km = 1000 m

1 h = 3600 s

So, $v=54 \frac{\mathrm{km}}{\mathrm{h}}=54\times \frac{1000 \mathrm{m}}{3600 \mathrm{s}}=\frac{540}{36 }\mathrm{m}/\mathrm{s}$

$\therefore v =54 \mathrm{km}/\mathrm{h} = 15 \mathrm{m}/\mathrm{s}$
 

Answer:

The Green Revolution refers to a period when technologically advanced methods were introduced in the field of agriculture for improving the yield. Green Revolution made its way into the Indian agricultural field in late 1960s. High Yielding Varieties (HYV) of seeds of wheat and rice were used by Indian farmers for increasing production. In addition, the use of fertilizers and pesticides greatly improved the overall yield and made India self-sufficient in food grain production.

The common objectives of crop improvemnt are -
 

Answer:

(a) Atoms of incense stick when lighted get mixed with the particles of air. Then we are able to smell its fragrance.
This shows that atoms intermix with each other and the process is known as diffusion.

(b) Due to the diffusion of gases, particles of food cooking in the kitchen get mixed with air. Due to diffusion particles move from higher concentration to the lower concentration, so the smell of food reached her brother's room.

Answer:

(a) The isotope of hydrogen is chemically similar because isotopes of the atom of the same element have the same atomic number but the different mass number. As the electronic configuration is the same. Due to this, there will be the same valence electrons and they have the same chemical properties.

(b) The isotopes of the hydrogen atom are electrically neutral because the number of protons and the number of electrons is equal. They both cancel out their charges resulting in the net charge zero.
 

Answer:

The initial velocity of the car = 20 ms⁻¹ 

The final velocity of the car = 0

Time taken by the car to stop = 10 s

Using the first equation of motion, we can write, $v = u + at$

So,
 $0 = 20+ a\times 10$

$\Rightarrow a =-2 {\mathrm{ms}}^{-2}$

Hence, retardation is 2 ms^-2. 

Retarding force = mass $\times$ retarding acceleration
                         = 2400 kg $\times$ 2 ms^-2 
                              = 4800 kg ms^-2
                              = 4800 N

Answer:

(a) Simple ion is formed due to gain or loss of electrons by a single atom of an element, For eg. Na^$+$, K^$+$, Mg^$+$2, etc.
A compound ion is formed due to excess anions or cations in a compound. For eg. ammonium ions (NH₄^$+$), carbonate ions(CO₃^$-$2), etc.

(b) (i) As Y has four valence electrons, it will form four single bonds with a chlorine atom and form YCl_4.
(ii) As Y has four valence electrons, it will form two double bonds with an oxygen atom and form YO_2.
(iii) As Y has four valence electrons, it will form two double bonds with sulfate atom and form Y(SO₃)_2.
(iv) As Y has four valence electrons, it will form two double bonds with carbonate and form Y(CO₃)₂.
(v)  As Y has four valence electrons, it will form four single bonds with nitrate and form Y(NO₃)₄.
 

Answer:

(a) Radioactive isotopes are those isotopes of an element which have an unstable nucleus. Because of this, the radioactive isotopes undergo radioactive decay by emitting alpha, beta, and gamma radiation to gain the stability of the nucleus. For eg, O¹⁵, Co⁶⁰, etc.

(b) Uses of radioactive isotopes:
(i) Radioactive isotopes are used to determine the age of rocks and minerals.
(ii) It is used to treat cancer, detect blood clots and diagnose thyroid.

(c) Let the percentage of ${}_{17}{}^{35}\mathrm{Z}$ = X
Then the percentage of ${}_{17}{}^{37}\mathrm{Z}$ = 100 $-$ X
Average atomic weight of Z = 35.5u
Now, 
$$\begin{gathered} 35.5=\frac{35.\mathrm{X}+37.(100-\mathrm{X})}{100} \\ \Rightarrow 35.5=\frac{35\mathrm{X}+3700-37\mathrm{X}}{100} \\ \Rightarrow 35.5\times 100=3700-2\mathrm{X} \\ \Rightarrow 3550-3700=-2\mathrm{X} \\ \Rightarrow -150=-2\mathrm{X} \\ \Rightarrow \mathrm{X}=75 \end{gathered}$$

Therefore, ${}_{17}{}^{35}\mathrm{Z}$ = 75% and, ${}_{17}{}^{37}\mathrm{Z}$ = 100$-$75 = 25%

Answer:

Pteridophytes belong to the phylum of plants. These are the first plants which show the presence of vascular tissues. They reproduce through spores instead of seeds.
 

Answer:

Some important viral diseases of humans are - Hepatitis, Polio, Rabies and AIDS.

1. Hepatitis - 
Causal organism - Hepatitis virus
Mainly affects liver and usually results in jaundice.
There are different types of hepatitis - hepatitis A,  hepatitis B,  hepatitis C,  hepatitis D,  hepatitis E.

Mode of transmission -

• Hepatitis A - spreads through contaminated food and water.
• Hepatitis B - spreads through contact with infected person's secretions such as saliva, sweat, tears etc.

Symptoms -

• Fever
• Nausea and vomiting
• Jaundice
• Dark yellow urine
• Itching of skin

Prevention -

• Eating hygenic food and drinking disinfected water
• Immunisation with hepatitis B and hepatitis A vaccines
• Use of disposable syringes
• Proper cleaning of hands after handling bed, clothes and utensils of the pateints

2. Polio
Causal organism - Polio virus
Mainly affects the children 

Modes of transmission -

• Spreads through faecal-oral route

Symptoms -

• Headache and fever
• Stiffness of the neck and convulsions
• Paralysis of limbs due to damage of motor nerve cells in the spinal cord
• Respiratory failure

Prevention -

• Immunization with oral polio vaccine

3. Rabies
Causal organism - Rabies virus named Lyssavirus.

Modes of transmission -

• Spreads through the bite of an infected animal such as dogs or cats.

Symptoms -

• Severe headache and high fever
• Painful contractions of muscles of throat and chest
• Hydrophobia, where an individual is afraid of water

Prevention -

• Vaccination of pet dogs and cats
• Cleaning the wound with soap and clean running water

4. AIDS -
Affects the immune system of the body

Causal organism - Human Immuno Virus (HIV)

Modes of Transmission -

• By sharing infected needles while injecting drugs.
• By having sexual contact with an infected person.
• From an infected mother to the child through pregnancy or breast feeding.

• Weight loss
• Prolonged fever
• Prolonged diarrhoea
• Kaposi’s sarcoma
• Meningitis
• Complete loss of immunity with infections like tuberculosis and pneumonia, etc.

Prevention -

• Education about the disease
• Use of disposable needles and syringes
• Avoiding sharing of razors for shaving
• Protected sexual intercourse using condoms
   

Answer:

The value of acceleration due to gravity is given by the relation, $g=\frac{GM}{R^2}$ (Where 'M' is the mass and 'R' is the radius of the planet)

Mass of the planet = 6$\times$10²⁴ kg

The radius of the planet = $\frac{\mathrm{Diameter}}{2}=\frac{12.8\times {10}^3 \mathrm{km}}{2}=6.4\times {10}^3 \mathrm{km}$

Gravitational constant = 6.7 $\times$10^$-$11 Nm²/kg²

So, $g=\frac{6.7\times {10}^{-11} {\mathrm{Nm}}^2{\mathrm{kg}}^{-2 }\times 6\times {10}^{24} \mathrm{kg}}{(6.4\times {10}^3\times {10}^3 \mathrm{m}{)}^2}=9.8 {\mathrm{ms}}^{-2}$

This planet could be earth because the value of acceleration due to gravity is the same on the planet earth.
 

Answer:

(a) Commercial unit of energy in 1 kWh. One kilowatt-hour is the amount of energy consumed in one hour at a constant rate of one kilowatt. SI unit of energy is joule.

$$\begin{gathered} 1 \mathrm{kWh}= 1 \mathrm{kW} \times 1 \mathrm{h} = 1000 \mathrm{W} \times 1 \mathrm{h} \\ =1000\left(\raisebox{1ex}{$\mathrm{J}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.\right) \times 3600 \mathrm{s} (\because 1 \mathrm{W} = 1 \raisebox{1ex}{$\mathrm{J}$}\!\left/ \!\raisebox{-1ex}{$\mathrm{s}$}\right.) \\ = 3600000 \mathrm{J} \\ 1 \mathrm{kWh}= 3.6\times {10}^6 \mathrm{J} \end{gathered}$$

(b) Energy consumed by certain household = 650 units = 650 kWh

$1 \mathrm{kWh}= 3.6\times {10}^6 \mathrm{J}$

$650 \mathrm{kWh}= 650\times 3.6\times {10}^6 \mathrm{J}=2.34\times {10}^9 \mathrm{J}$

Answer:

Tincture of iodine is prepared by dissloving proper amount of iodine(solid) in an alcohol solution.

(a) So X would be alcohol.

(b) So Y would be iodine.

(c) When the solid phase directly converts to gas phase on heating, it is known as sublimation. So process Z is sublimation.

(d) By fractional distillation method, we can easily separate both the components. As there is a difference in the boiling point of two solutions.

(e) By evaporation method, we can easily separate the component Y(Iodine) from the given sample.

Answer:

(a) First of all, bat is not a type of bird. It belongs to the category of mammals. It has patagia in the forelimbs which functions as wings and helps in the flight of bat.

(b) Bat is an animal which does not require sharp vision to see during night. It depends on ecowaves which it sends to interpret an obstacle (ecolocation).

(c) Bats feed nocturnal insects (insects which fly in night). Bats detect these insects based on sound waves produced by them. It is also one of the ways of biologically controlling the population of these insects.

Answer:

When we are ill, our normal body functions get disturbed. In order to recover, we need a nutritious meal which is easily digestable and contains all the nutrients. So. it is advised to have bland and nourishing food.

Answer:

The formula of carbonate of a metal M is M₂CO₃.
Valency of carbonate is 2
As here two metals are present, 
So, the valency of metal, M is 1.

(a) Valency of iodide is 1.
So, the formula for iodide of metal M will be MI.

(b) Valency of nitrogen is 3.
So, the formula for nitride of metal M will be M₃N.

(c) Valency of phosphate is 3.
So, the formula for the phosphate of metal M will be M₃PO₄.

Answer:

If a coin and a piece of paper are dropped simultaneously from the same height in the air, then the coin will touch the ground first and the paper will touch later. Because the paper will experience an air resistance due to its lightweight whereas coin has more weight, so air resistance won't affect coin.

But if the same coin and paper are dropped simultaneously in a vacuum then both the coin and the paper will reach the ground at the same time, because in a vacuum there will not be any kind of air resistance and gravity will take them both down at the same time.

Answer:

(a) In the given case, the mechanical energy of the ball will always remain conserved. Hence, the sum of the potential energy and the kinetic energy will always remain constant.

At the highest point A, total mechanical energy = Potential energy + Kinetic energy = 80 J + 0 J = 80 J

At the lowest point, total mechanical energy =  total mechanical energy at the highest point

So, at the lowest point, Potential energy + Kinetic energy  = 80 J = 0 + Kinetic energy

Hence, at the lowest point, kinetic energy is 80 J.

(b) As we know that mechanical energy is constant throughout the motion.

So, mechanical energy at point B = Mechanical energy at point A

Mechanical energy at point B  = Potential energy at point B + Kinetic energy at point B = 80 J

Potential energy at point B = 80 J $-$ 48 J = 32 J

(c) The law of conservation of mechanical energy has been used while answering the above questions.