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Force and Laws of Motion — Science STD 9 — Question

Gujarat BoardEnglish MediumSTD 9ScienceForce and Laws of Motion4 Marks
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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Instruction: The table given below shows distance (in cm) travelled by the bodies A, B and C. Read this data carefully and answer the questions which follow.
Distance (in cm) covered by different bodies:
Time
Body A
Body B
Body C
1st second
20
20
20
2nd second
20
36
60
3rd second
20
24
100
4th second
20
30
140
5th second
20
48
180
  1. Which of the bodies is moving with:
  1. Constant speed?
  2. Constant acceleration?
  1. Which of the bodies covers:
  1. Maximum distance in 3rd second?
  2. Minimum distance in 3rd second?
  1. Which of the bodies is moving with non-uniform acceleration?
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The growth of plants occurs only in certain specific regions. This is because the dividing tissue, also known as meristematic tissue, is located only at these points. Depending on the region where they are present, meristematic tissues are classified as apical, lateral and intercalary. New cells produced by meristem are initially like those of meristem itself, but as they grow and mature, their characteristics slowly change and they become differentiated as components of other tissues

Apical meristem is present at the growing tips of stems and roots and increases the length of the stem and the root. The girth of the stem or root increases due to lateral meristem (cambium). Intercalary meristem seen in some plants is located near the node

Cells of meristematic tissue are very active, they have dense cytoplasm, thin cellulose walls and prominent nuclei. They lack vacuoles.

(1) Which meristem helps in increasing the girth of the plant?

(a) Primary meristem

(b) Apical meristem

(c) Intercalary meristem

(d) Lateral meristem

(2) Lateral meristem is responsible for_____________

(a) Growth of apical portion

(b) Increase in the length

(c) Increasing the girth of stem and root

(d) Growth in parenchyma

(3) The meristem present at the base of the internode is_____________

(a) Lateral meristem

(b) Intercalary Meristem

(c) Apical Meristem

(d) All of the above

(4) What are the characteristic of Meristematic tissue?

(5) Enlist the type of meristematic tissue.

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 A violin and a flute may both be played the same time in an orchestra. Bothsounds travel through the same medium,that is, air and arrive at our ear at the sametime. Both sounds travel at the same speedirrespective of the source. But the soundswe receive are different. This is due to thedifferent characteristics associated with thesound. Pitch is one of the characteristics.How the brain interprets the frequency ofan emitted sound is called its pitch. The fasterthe vibration of the source, the higher is the frequency and the higher is the pitch. The magnitude of the maximumdisturbance in the medium on either side ofthe mean value is called the amplitude of thewave. It is usually represented by the letter (A).

The loudness or softness of a sound isdetermined basically by its amplitude. Theamplitude of the sound wave depends uponthe force with which an object is made tovibrate. If we strike a table lightly, we hear asoft sound because we produce a sound waveof less energy (amplitude).

The quality or timber of sound is thatcharacteristic which enables us to distinguishone sound from another having the same pitchand loudness. The sound which is morepleasant is said to be of a rich quality. A sound of single frequency is called a tone. The sound which is produced due to a mixture of several frequencies is called a note and is pleasant to listen to. Noise is unpleasant to the ear! Music is pleasant to hear and is of rich quality.

(i) Pitch of sound is higher when

(a) Vibration of source of sound is higher

(b) Vibration of source of sound is Lower

(c) Independent of vibration of source of sound

(d) None of these

(ii) Loudness and softness of sound depends upon

(a) Frequency of sound

(b) Amplitude of sound

(c) Wavelength of sound

(d) None of these

(iii) Sound of single frequency is called

(a) Note

(b) Tone

(c) Noise

(d) None of these

(iv)If we strike a table lightly, we hear asoft sound. If we hit the tablehard we hear a louder sound up to large distance. Why?

(v) Determine which of the following has higher pitch railway horn or guitar?

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The force acting on an object perpendicular to the surface is called thrust. When you stand on loose sand, the force, that is, the weight of your body is acting on an area equal to area of your feet. When you lie down then the same force acts on an area equalto the contact area of your whole body, which is larger than the area of your feet. Thus, the effects of forces of the same magnitude on different areas are different. In the above cases, thrust is the same. But effects are different. Therefore the effect of thrust depends on the area on which it acts. The effect of thrust on sand is larger while standing than while lying. The thrust on unit area is called pressure.

Pressure=thrust/area. SI unit of pressure as N/m2or Pascal.

(i) SI unit of thrust is

(a) m/s

(b) m/s2

(c) Newton(N)

(d) None of these

(ii) We have two different areas A and B. where A>B. Then relation between pressure on A(PA) and pressure on B (PB) is

(a) PA>PB

(b) PB>PA

(c) PA=PA

(d) None of these

(iii)SI unit of pressure is

(a) N/m2

(b) Pascal.

(c) Both a and b

(d) None of these

(iv) The effects of forces of the same magnitude on different areas are different. True or false

(a) True

(b) False

(c) None of these

(v) Define pressure.

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Many indigestion mixtures are suspensions. What do the instructions written on the bottle of an indigestion mixture tell us before taking the mixture, and why?
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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.
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  2. What type of change occurs when sold D is dissolved in water? Why?
  3. Name a metal which you think could behave like solid A. Also name the products B and C.
  4. Name the solid D if it is the one which is used in making ordinary dry cells.
  5. Name the process by which D can be recovered from E.
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Rutherford (1871-1937) was known as the ‘Father’ of nuclear physics. He is famous for his work on radioactivity and the discovery of the nucleus of an atom with the gold foil experiment. Ernest Rutherford was interested in knowing how the electrons are arranged within an atom. Rutherford designed an experiment for this. In this experiment, fast moving alpha (α)-particles were made to fall on a thin gold foil. On the basis of his experiment, Rutherford put forward the nuclear model of an atom, which had the following features:

  • There is a positively charged centre in an atom called the nucleus. Nearly all the mass of an atom resides in the nucleus.
  • The electrons revolve around the nucleus in circular paths.
  • The size of the nucleus is very small as compared to the size of the atom.

Drawbacks of Rutherford’s model of the atom: The revolution of the electron in a circular orbit is not expected to be stable. Any particle in a circular orbit would undergo acceleration. During acceleration, charged particles would radiate energy. Thus, the revolving electron would lose energy and finally fall into the nucleus. If this were so, the atom should be highly unstable and hence matter would not exist in the form that we know. We know that atoms are quite stable.

(1) Which of the following scientist was known as the ‘Father of nuclear physics?

(a) J.J. Thomson

(b) John Dalton

(c) E. Rutherford

(d) Neilsbhore

(2) Positively charged centre in an atom is termed as

(a) Nucleus

(b) Molecule

(c) Atom

(d) Protons

(3) Identify the correct statement

Statement 1 – Positively charged centre in an atom called the nucleus.

Statement 2 – The electrons revolve around the nucleus in circular paths.

Statement 3 – Nearly all the mass of an atom resides in the nucleus.

Statement 4 – The size of the nucleus is very small as compared to the size of the atom.

(a) Only 2

(b) Both 3 & 4

(c) Both 1 & 2

(d) All of the above

(4) Write the features of Rutherford’s nuclear model of an atom?

(5) Define Nucleus.

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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.

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In the given below activity, on heating the solution, water evaporates, and we get back the ink dye in the watch glass. The different substance has a different boiling point. We use this property to separate the components of the mixture. Here, the boiling point of ink is much higher than that of water. On heating the ink solution, water evaporates while ink dye remains in the china dish.

(i) Name the process shown in the diagram.

(a) Boiling(b) Filtration(c) Crystallisation(d) Distillation

(ii) Which type of substance can be separated by this method ?
(a) Any solvent from its non-volatile solute.
(b) The volatile solvent from its non-volatile solute.
(c) The non-volatile solvent from its non-volatile solute.
(d) The volatile solvent from its volatile solute.
(iii) What can we interpret about the nature of ink ?

(a) We cannot separate components of ink(b) Ink is not a mixture
(c) Ink is pure substance(d) Ink is a mixture of dyes in water.

(iv) Name the component which gets evaporated.
(a) Heating leads to the evaporation of water.
(b) Heating leads to the evaporation of dyes.
(c) Heating leads to the filtration of water.
(d) Heating leads to the distillation of dyes.


(v) Define the process shown in the diagram
(a) It is the process of conversion of a liquid into its vapours.
(b) It is a process of separating insoluble component by filtering the solution
(c) It is a process that separates a pure solid in the form of its crystals
(d) It is a technique to separate two miscible liquids

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Blood is a type of connective tissue. The cells of connective tissue are loosely spaced and embedded in an intercellular matrix. The matrix may be jelly like, fluid, dense or rigid. The nature of matrix differs in concordance with the function of the particular connective tissue.

Blood has a fluid (liquid) matrix called plasma, in which red blood corpuscles (RBCs), white blood corpuscles (WBCs) and platelets are suspended. The plasma contains proteins, salts and hormones. Blood flows and transports gases, digested food, hormones and waste materials to different parts of the body.

Bone is another example of a connective tissue. It forms the framework that supports the body. It also anchors the muscles and supports the main organs of the body. It is a strong and nonflexible tissue. Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds. Two bones can be connected to each other by another type of connective tissue called the ligament. This tissue is very elastic.

Another type of connective tissue, cartilage, has widely spaced cells. The solid matrix is composed of proteins and sugars. Cartilage smoothens bone surfaces at joints and is also present in the nose, ear, trachea and larynx.

Areolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in the bone marrow. It fills the space inside the organs, supports internal organs and helps in repair of tissues.

(1) A connective tissue

(a) Has no matrix

(b) Covers the skin

(c) Has abundant matrix

(d) None of these

(2) Areolar connective tissue is found between

(a) Skin and muscles

(b) Blood vessels and nerves

(c) Both a & b

(d) None of these

(3) Two bones are connected to each other by another type of connective tissue called__

(a) Ligament

(b) Cartilage

(c) Bone marrow

(d) Blood

(4) What are the function of connective tissue?

(5) Give the examples of connective tissue.

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