885 + Interview Questions in Physics in Class 8 Page 14 InterviewSolution

651.	An empty density bottle weighs 30 g, and 54 g when filled with kerosene. If the volume of the bottle is 30 ml, find the density of kerosene in (a) "g/cm"^3 (b)"kg/m"^3 .Alsofind its RD.
Answer» ANSWER :(a)`0.8 "g/cm"^3` (B)`800 "kg/m"^3` ; RD=0.8

Discussion

652.	Fill in the blanks : 3. Sound cannot travel through________.
Answer» ANSWER :A::C

Discussion

653.	Which of these is not effected in an object when force is applied on it?
Answer» Shape Speed Direction Weight Answer :D

Discussion

654.	What are the factors which differentiate sound from each other?
Answer» Answer :AMPLITUDE and FREQUENCY are the two IMPORTANT FACTORS which differentiate ONE sound from the other.

Discussion

655.	Choose the correct answer. Sound can travel through
Answer» GASES only solids only LIQUIDS only solids, liquids and gases Answer :D

Discussion

656.	Hydrogen gas which is easily available on the earth is going to be the next promising fuel ' -discuss.
Answer» Solution :(i) Calorific value of hydrogen gas. Advantage and disadvanteges of hydrogen gas as a fuel. (ii) Find the calorific value of hydrogen as a fuel. Find the pollutants released due to the combustion of hydrogen. Is stream (water vapour) a toxic substance ? can a TECHNOLOGY in whic hydrogen is used as fuel be developed ? is it already in use ? how are ROCKETS SENT into OUTER space ?

Discussion

657.	Do you notice that each of the actions can be grouped as a pull or a push or both? Can we infer from thisa, that to move an object, it has to be pushed or pulled?
Answer» ANSWER :Yes, each of the ACTIONS can be grouped as a pull or a push or both.Yes, from the above observation we can INFER that to move an object, it has to be pushed or PULLED.

Discussion

658.	Sometimes, a cracking sound is heard while taking off a sweater during winters. Explain.
Answer» Answer :Sometimes, a cracking sound is heard while TAKING off a sweater during winters because when our hair is rubbed with the woolen sweater, it gets charged. Since the hair and the woolen sweater are MADE of different MATERIALS.

Discussion

659.	Fill in the blanks : The process of depositing a layer of any desired metal on another material by means of electricity in called ____.
Answer» ANSWER :electroplanting

Discussion

660.	A spanner is used to unscrew a nut. A force of 30 N is applied to the end of the spanner, which is 10 cm away from the centre of the nut. Calculate the moment of force when the spanner is horizontal.
Answer» Solution :To Calculate the moment of force , USE the FORMULA : `tau = F xx d` F=30 N and d=10 cm = 0.1 m `tau`= 30 x 0.1 = 3 Nm

Discussion

661.	Choose the càrrect oplion in Questions. Image formed by a plane mirror is
Answer» VIRTUAL, behind the mirror and enlarged. virtual, behind the mirror and of the same SIZE as the object. real at the SURFACE of the mirror and enlarged. real, behind the mirror and of the same size as the object. Answer :B

Discussion

662.	What is cataract?
Answer» ANSWER :Cataract is a disease which occurs particularly in old age when the PERSON’s eyesight becomes FOGGY or he MAY become VISUALLY impaled. This disease occurs because the eye lens become opaque and cloudy.

Discussion

663.	Fill in the blanks: Jewellery makers electroplate ___ and __ on less expensive metals.
Answer» ANSWER :GOLD,SILVER

Discussion

664.	Four children were asked to arrange forces due to rolling, static and sliding frictionsin a decreasing order. Their arrangements are given below. Choose the correct arrangement.
Answer» ROLLING, STATIC, SLIDING rolling, sliding, static static, sliding, rolling sliding, static, rolling Answer :C

Discussion

665.	How many images of a candle will be formed If it is placed between two parallel plane mirrors separated by 40 cm?
Answer» Answer :Infinite/innumerable IMAGES of the candle will be formed if it is placed between TWO plane MIRRORS SEPARATED by 40 cm.

Discussion

666.	What is the measurement of rolling friction?
Answer» Answer :Measurement of ROLLING friction is the resistance applied to the MOTION of a rolling body over the SURFACE of ANOTHER body.

Discussion

667.	A bar magnet and a soft iron bar AB are placed close to each other as shown below Mark the polarity of induced magnetism in the soft iron bar with the help of lines of force. Explain by giving reasons for the polarity marked by you.
Answer» Solution :Map the magnetic lines of force in the magnetic field of a bar MAGNET . What is the DIRECTION of magnetic lines of force in the soft IRON rod ? Identify the magnetic POLES by USING the direction of magnetic lines of force inside the iron bar.

Discussion

668.	Fill in the blanks : Force arises due to ______ between two objects.
Answer» ANSWER :INTERACTION.

Discussion

669.	Fill in the blanks. ___are the materials which allow electric current to pass through them.
Answer» conductor insulator both a and b NONE of these Answer :none

Discussion

670.	The attracting power of a magnet is
Answer» EVENLY DISTRIBUTED ALONG its length. maximum at its centre. maximum at its poles minimum at its poles. Answer :C

Discussion

671.	If a pendulum clock loses time, then the length of the pendulum should be appropriately decreased.
Answer» ANSWER :TRUE

Discussion

672.	Magnetic field lines inside a solenoid
Answer» are PARALLEL to each other are convergent are divergent None of the above Answer :A

Discussion

673.	If the focal length of a concave mirror is 14 cm, what would be its radius of curvature?
Answer» ANSWER :28 CM

Discussion

674.	Fill in the blanks- with suitable words. Shrillness of a sound is determined by the ____________ of vibration.
Answer» ANSWER :C

Discussion

675.	A clean hole is made in a glass window pane when it is struck by a bullet fired from a gun. Whereas, the same window pane will be broken to pieces when struck by a stone of a similar size. Explain this phenomenon quoting the relevant principles.
Answer» SOLUTION :Which one AMONG the following (i.e.,) bullet fired from a gun or a STONE of similar size will have greater VELOCITY? From this information, which one will have more momentum? Is INERTIA of motion for bullet more than that of stone? Is the impulsive force exerted by bullet more? In which case is the foce exerted on the window pane more?

Discussion

676.	As your parents about the huge damage to life and property cause by these earthquakes from newspapers and magazines of those days. Prepare a short report on the suffering of the people during and after the earthquakes.
Answer» ANSWER :STUDENTS should do themselves.(i) PHYSICAL damage(ii) CASUALITIES(iii) Public health.

Discussion

677.	Fill in the blanks: Filament of the bulb glows due to the ___ of current.
Answer» ANSWER :HEATING EFFECT

Discussion

678.	Magnetic lines of force are directed from______pole to ____pole, in the magnetic field
Answer» ANSWER :NORTH, SOUTH

Discussion

679.	Two containers X and Y are filled with water at different temperature. When 10 g of water from container X is mixed with 20 g of water from container Y, the resultant temperature is found to be 20^(@)C. When 20 g of water from container X is mixed with 10 g of water from container Y, the resultant temperature is found to be 30^(@)C. Determine the inital temperature of water in container X and Y.
Answer» Solution :heat LOST by the body at higher temperature=heat GAINED by the body at LOWER temperature. Q=`msDeltat`

Discussion

680.	State whether the following statement is true or false: Liquids and gases exert pressure on the walls of the container.
Answer» ANSWER :1

Discussion

681.	The direction of magnetic field at any point inside the field is given by _________.
Answer» PERPENDICULAR to the LINE of FORCE tangent to the line of force the line of force itself none of the above Answer :B

Discussion

682.	When the coin is held in your hand it is at rest. As soon as it is released, it begins to move downwards. It is clear that the state of motion of the coin undergoes a chamge. Can this happen without a force acting on it? Which is this force?
Answer» ANSWER :No, the coin cannot move on its own WITHOUT a force ACTING on it,

Discussion

683.	Looking at the angle of refraction in the figures given Fig. B, which medium will have the maximum value of refractive index and in which medium will the speed of light be the least?
Answer» Solution :When `ANGLER` is more, speed of light is more , and refractive INDEX is LESS.

Discussion

684.	State whether the following statements are true or false : Venus shows phases just like the moon.
Answer» ANSWER :1

Discussion

685.	Fill in the blanks : If there were no friction, amoving object wouldnever ________
Answer» ANSWER :STOP

Discussion

686.	Are all celestial objects similar?
Answer» Answer :No, all CELESTIAL OBJECTS are not similar. They DIFFER in their shape.size,location, COLOUR,etc.

Discussion

687.	A man standing on one leg is an example of ______.
Answer» UNSTABLE EQUILIBRIUM STABLE equilibrium neutral equilibrium Both (b) and (C ) Answer :A

Discussion

688.	Every form of energy manifested on the earth is dependent on solar energy either directly or indirectly. Is this true in case of fossil fuels.
Answer» Solution :(i) MEANING of FOSSIL fuels. (II) Their FORMATION.

Discussion

689.	Fill in the blanks : _________ sound is one which is pleasing to the ear.
Answer» ANSWER :A::C

Discussion

690.	The vertical plane in which magnetic needle lies at a place is called______
Answer» GEOGRAPHICAL meridian magnetic equator geographical equator magnetic meridian Answer :D

Discussion

691.	_________is the energy liberated when its unit mass is burnt completely.
Answer» ANSWER :CALORIFIC VALUE

Discussion

692.	What is reflected ray?
Answer» Answer :A reflected ray is the ray of LIGHT that BOUNCES back into same MEDIUM after reflection at the POINT of INCIDENCE.

Discussion

693.	What should be done to minimise fluid friction?
Answer» ANSWER :SPECIAL SHAPES are GIVEN to objects to minimise fluid friction.

Discussion

694.	{:(,"Column A",,,"Column B"),(A.,"Dyne","()",a.,"Maximum static friction"),(B.,"Momentum","()",b.,"Mechanical advantage is two"),(C.,"Inertia","()",c.,"Newton's third law"),(D.,"Mass","()",d.,"Centroid of the triangle"),(E.,"Limiting friction","()",e.,"Newton's first law"),(F.,"C.G. of a triangular lamina","()",f.,"Lever of third order"),(G.,"kg m s"^(-2),"()",g.,"CGS unit of force"),(H.,"Forceps","()",h.,"Mass"xx"veloctiy"),(I.,"Working of rocket","()",i.,"Scalar quantity"),(J.,"Single movable pulley","()",j.,"newton"):}
Answer» Answer :`"A : GB : hC : ED : iE : AF : DG : JH : fI : cJ : b"`

Discussion

695.	Boojho remembered that in Class VII, he had studied some features of the image of an object formed by a plane mirror. Paheli asked him to recall those features : Was it of the same size as theobject?
Answer» ANSWER :YES, the IMAGE was of the same SIZE as the OBJECT.

Discussion

696.	Boojho remembered that in Class VII, he had studied some features of the image of an object formed by a plane mirror. Paheli asked him to recall those features : (i) Did the image appear at the same distance behind the mirror as the object was in front of it? (ii) Could it be obtained on a screen?
Answer» ANSWER :(i) YES,the image appeared at the same distance behind the mirror as the OBJECT was in FRONT of it. (ii) No, it COULD not be obtained on a screen because it was a virtual image.

Discussion

697.	Boojho remembered that in Class VII, he had studied some features of the image of an object formed by a plane mirror. Paheli asked him to recall those features : Was the image erect or upsidedown?
Answer» ANSWER :The IMAGE was ERECT.

Discussion

698.	State whether the following statements are true or false : Sound of a bird is high-pitched and that of a lion is low-pitched.
Answer» ANSWER :A

Discussion

699.	What is lubricant?
Answer» Answer :A substance used to reduce friction between the surfaces o F TWO objects in contact is CALLED lubricant. For example, oil, GREASE, fine powder, air CUSHION, etc.

Discussion

700.	What is the unit of measurement of frequency?
Answer» Answer :FREQUENCY is MEASURED in HERTZ, which is expressed as HZ.

Discussion

Explore topic-wise InterviewSolutions in .

An empty density bottle weighs 30 g, and 54 g when filled with kerosene. If the volume of the bottle is 30 ml, find the density of kerosene in (a) "g/cm"^3 (b)"kg/m"^3 .Alsofind its RD.

Fill in the blanks : 3. Sound cannot travel through________.

Which of these is not effected in an object when force is applied on it?

What are the factors which differentiate sound from each other?

Choose the correct answer. Sound can travel through

Hydrogen gas which is easily available on the earth is going to be the next promising fuel ' -discuss.

Do you notice that each of the actions can be grouped as a pull or a push or both? Can we infer from thisa, that to move an object, it has to be pushed or pulled?

Sometimes, a cracking sound is heard while taking off a sweater during winters. Explain.

Fill in the blanks : The process of depositing a layer of any desired metal on another material by means of electricity in called ____.

A spanner is used to unscrew a nut. A force of 30 N is applied to the end of the spanner, which is 10 cm away from the centre of the nut. Calculate the moment of force when the spanner is horizontal.

Choose the càrrect oplion in Questions. Image formed by a plane mirror is

What is cataract?

Fill in the blanks: Jewellery makers electroplate ___ and __ on less expensive metals.

Four children were asked to arrange forces due to rolling, static and sliding frictionsin a decreasing order. Their arrangements are given below. Choose the correct arrangement.

How many images of a candle will be formed If it is placed between two parallel plane mirrors separated by 40 cm?

What is the measurement of rolling friction?

A bar magnet and a soft iron bar AB are placed close to each other as shown below Mark the polarity of induced magnetism in the soft iron bar with the help of lines of force. Explain by giving reasons for the polarity marked by you.

Fill in the blanks : Force arises due to ______ between two objects.

Fill in the blanks. ___are the materials which allow electric current to pass through them.

The attracting power of a magnet is

If a pendulum clock loses time, then the length of the pendulum should be appropriately decreased.

Magnetic field lines inside a solenoid

If the focal length of a concave mirror is 14 cm, what would be its radius of curvature?

Fill in the blanks- with suitable words. Shrillness of a sound is determined by the ____________ of vibration.

A clean hole is made in a glass window pane when it is struck by a bullet fired from a gun. Whereas, the same window pane will be broken to pieces when struck by a stone of a similar size. Explain this phenomenon quoting the relevant principles.

As your parents about the huge damage to life and property cause by these earthquakes from newspapers and magazines of those days. Prepare a short report on the suffering of the people during and after the earthquakes.

Fill in the blanks: Filament of the bulb glows due to the ___ of current.

Magnetic lines of force are directed from______pole to ____pole, in the magnetic field

State whether the following statement is true or false: Liquids and gases exert pressure on the walls of the container.

The direction of magnetic field at any point inside the field is given by _________.

When the coin is held in your hand it is at rest. As soon as it is released, it begins to move downwards. It is clear that the state of motion of the coin undergoes a chamge. Can this happen without a force acting on it? Which is this force?

Looking at the angle of refraction in the figures given Fig. B, which medium will have the maximum value of refractive index and in which medium will the speed of light be the least?

State whether the following statements are true or false : Venus shows phases just like the moon.

Fill in the blanks : If there were no friction, amoving object wouldnever ________

Are all celestial objects similar?

A man standing on one leg is an example of ______.

Every form of energy manifested on the earth is dependent on solar energy either directly or indirectly. Is this true in case of fossil fuels.

Fill in the blanks : _________ sound is one which is pleasing to the ear.

The vertical plane in which magnetic needle lies at a place is called______

_________is the energy liberated when its unit mass is burnt completely.

What is reflected ray?

What should be done to minimise fluid friction?

Boojho remembered that in Class VII, he had studied some features of the image of an object formed by a plane mirror. Paheli asked him to recall those features : Was it of the same size as theobject?

Boojho remembered that in Class VII, he had studied some features of the image of an object formed by a plane mirror. Paheli asked him to recall those features : (i) Did the image appear at the same distance behind the mirror as the object was in front of it? (ii) Could it be obtained on a screen?

Boojho remembered that in Class VII, he had studied some features of the image of an object formed by a plane mirror. Paheli asked him to recall those features : Was the image erect or upsidedown?

State whether the following statements are true or false : Sound of a bird is high-pitched and that of a lion is low-pitched.

What is lubricant?

What is the unit of measurement of frequency?

Fill in the blanks: Jewellery makers electroplate _ and on less expensive metals.

Magnetic lines of force are directed from__pole to pole, in the magnetic field