885 + Interview Questions in Physics in Class 8 Page 11 InterviewSolution

501.	Fill in the blanks- with suitable words. Time taken by an object to complete one oscillation is called ____________ .
Answer» ANSWER :D

Discussion

502.	What is the distance of the Sun from the Earth?
Answer» Answer :The SUN is SITUATED at a distance of 8 light minutes or 150 MILLION km away from the Earth.

Discussion

503.	When a Fortins barometer is used to measure the pressure on the surface of the earth and on the top of a building the main scale redaing is found to be the same and the vernier scale reading is found to be 9 and zero, respectively. If one M.S.D. is 1 mm and number of vernier scale divisions is 10, calculate the height of the building. Take the average density of air as 1.3 kg m^(-3), and that of mercury as 13.6 g cm^(-3)
Answer» Solution :(i) PRESSURE at the bottom of the BUILDING, `P_(1)=M.S.D._(1)+V.S.D._(1)+L.C.` Pressure at the top of the building, `P_(2)=M.S.D._(2)+V.S.D._(2)+L.C.` Pressure exerted by the air at the bottom and top of the building are `h_(1) dg" and " h_(2)dg`. Now, `P_(1)-P_(2)=(M.S.D._(1)+V.S.D._(1) xx L.C.)-M.S.D._(2)+V.S.D._(2) xx L.C.=(h_(1)-h_(2))dg` The HEIGHT of the building `(h_(2)-h_(1))` can be determined from the above equation (II) 941.5 cm (or) 9.4 m

Discussion

504.	A car changes its speed from 20 km h^(-1) to 50 km h^(-1). This is possible only if ______ is applied on the car.
Answer» ANSWER :EXTERNAL FORCE

Discussion

505.	The transverse waves can propagate through
Answer» both in a GAS and in a metal in a gas but not in a metal in a metal but not in a gas neither in a gas nor in a metal Solution :TRANSVERSE WAVES can travel through METALS but not through GASES

Discussion

506.	Fill in the blanks : Most liquids that conduct electricity are solutions of___,___ and ___.
Answer» ANSWER :ACIDS, BASES, SALTS

Discussion

507.	A machine does 392 J of work in 4 seconds. What is the power of the machine?
Answer» ANSWER :98 W

Discussion

508.	To protect buildings fromlightning , a good conductor of electricity like a copper rod, is used.
Answer» ANSWER :1

Discussion

509.	Describe Barometer
Answer» SOLUTION :N//A

Discussion

510.	The force involved in falling of an apple from a tree is known as _____
Answer» MAGNETIC FORCE electrostatic force contact force GRAVITATIONAL force ANSWER :gravitational force

Discussion

511.	A chargedthermocol ball is suspended by means of anylon thread.When a neutral bodyis brought nearer to it the thermocol ball is first attracted by it and then flies away from it. Explain by giving the reason.
Answer» Solution :What happens whencharged body is BROUGHT in CONTACT with an uncharged METALLIC body? What happens to the electrons present on the SURFACE of an uncharged body when a positivelycharged body is brought in contact with it ?

Discussion

512.	All mechanical forces are contact forces.
Answer» ANSWER :TRUE

Discussion

513.	If the distance between two successive compressions of a sound wave is 16 cm, then the distance between a compression and the next rarefactions is ______
Answer» 16 cm 32 cm 4 cm 8 cm Answer :D

Discussion

514.	An air bubble rises up in water because,
Answer» there is no gravity in WATER. pressure inside the BUBBLE is LESS than the pressure OUTSIDE it. the upthrust acting on the bubble is more than the weight of the bubble. air cannot DISSOLVE in water. Solution :An air bubble rises up in water because the upthrust acting on the bubble is more than the weight of the bubble.

Discussion

515.	What is night blindness?
Answer» Answer :Night blindness is a DISEASE caused DUE to deficiency of vitamin A when the patient cannot see CLEARLY in dim light.

Discussion

516.	Find out if there is an organisation in your area which provides relief to those suffering from natural disaster. Enquir. Enquire about the type of help they render to the victims of earthquakes. Prepare a brief report on the problems of the earth victims.
Answer» ANSWER :NGO's Non-governmental organisations provide relief to the PEOPLE SUFFERING from natural disasters such as EARTHQUAKES.

Discussion

517.	In an electric generator, the voltage induced across the terminals of the copper coil when it rotates in the magnetic field is
Answer» an ALTERNATING VOLTAGE direct voltage STEP up voltage step down voltage ANSWER :A

Discussion

518.	The north pole of a magnet is brought near a stationary negatively charged conductor. Will the pole experience any force?
Answer» ANSWER :INDUCTION,ATTRACTION

Discussion

519.	Choose the correct option(Multiple choice questions): ___is deposited on the positive electrode when current is passed through water.
Answer» COPPER Copper sulphate Oxygen Hydrogen Answer :C

Discussion

520.	The distance between the 1st crest and the 3^(rd) crest in a transverse wavve is 10 m. Find its wavelength
Answer» SOLUTION :`2 LAMDA = 10 m` `lamda = 5M` Wavelength = 5 m

Discussion

521.	Which among the following statement is/are correct?
Answer» The priciple of a bimetallic strip is unequal EXPANSION of metals. An iron ring is cooled to fix it on a wooden wheel. When the room temperature is RAISED, a PENDULUM clock loses time All of the above Solution :When a bimetallic strip is HEATED, it bends as one metal expands more than the other. Option (a) is correct. When iron ring is heated, it expands and when cooled, it contracts. Option (b) is correct. When the room temperature is increased, the length of the pendulum increases, and hence, the time period increases. therefore, it TAKES more time to complete one oscillation. so the pendulum clock loses time. Option (c) is correct.

Discussion

522.	When the mercury thread rises to 3/4th of the distance between the two fixed points, what is the temperature indicated by the Fahrenheit scale?
Answer» Solution :Consider the length of mercury THREAD between the two fixed points as 'l'. Then, `l=DeltaF=180^(@)F` . . .(1) Find `(3)/(4)l` by multipying `(3)/(4)` with `180^(@)F`(2) here, LFP for FAHRENHEIT scale is `32^(@)F`. So, add `32^(@)F` tot eh ANSWER obtaine din the equation (2). This becomes the temperature indicated by the fahrenheit scale, when the mercury thread RISES to (3/4) th of the distance between its two fixed points.

Discussion

523.	What causes the rectangularcoil in a D.C. motor to rotate? Explain.
Answer» Solution :Do the two VERTICAL SIDES of the coil of DC motor? What is the direction of the FORCES ACTING on Do the forces acting on the vertical sides constitute a COUPLE ? What is the effect of the couple?

Discussion

524.	Black surface is a
Answer» good ABSORBER of heat energy. good radiator o heat energy. Both a and b None of these Solution :Black SURFACE is a good absorber as WELL as good radiator of heat energy.

Discussion

525.	What are the advantages and disadvantages of using charcoal as a fuel as compared to wood ?
Answer» SOLUTION :CHARACTERISTICS of a GOOD FUEL.

Discussion

526.	Which of the following substance is repelled by strong magnet ?
Answer» Iron Platinum GOLD Aluminium Solution :Gold is a diamangnetic SUBSTANCE and it is REPELLED by MAGNETS.

Discussion

527.	When your teacher is writing with chalk on the blackboard, its rough surface rubs off some chalk particies with stick to-the blackboard. Could ithappen if there were no friction between the chalk and the board?
Answer» Answer :No, without FRICTION between the CHALK and the BOARD, it would not be possible to WRITE on the BLACKBOARD.

Discussion

528.	Fill in the blanks : ________controls the amount of light entering into the eye.
Answer» ANSWER :IRIS

Discussion

529.	A bird is sitting on the floor of a wire cage and the cage is in the hand of a boy . The bird starts flying in the cage . Will the boy experience any change in the weight of the cage ?
Answer» SOLUTION :(i) ACTION and reaction (ii) `20 G cm^(-3)`

Discussion

530.	Magnetic lines of force due to a straight conductor carrying current are
Answer» COAXIAL cylinders concentric circles parallel lines concentric spheres Answer :B

Discussion

531.	Take a used ballpen refill and rub it vigorously, with a piece of polythene. Bring it close to small pieces of paper. Take care not to touch the rubbed end of the refill with your hand or with a metallic object. Respect the activity with small pieces of dry leaf, husk and mustard seeds. Record your observations.
Answer» Answer :Observation :We OBSERVE that the RUBBED END of the refill attracts the small PIECES of paper, dry leaf, husk and mustard SEEDS.

Discussion

532.	A stone is immersed in a Eureka can. The mass of the empty beaker into which water overflowed was 30 g and the mass of the beaker with the water from the Eureka can is 56 g. If the mass of the stone is 87 g. What is the density of the stone?
Answer» SOLUTION :`m_1`=30 G , `m_2`=56 g , `m_2-m_1`=56-30=26 g Volume (V)=`26/1= 26 "CM"^3` m=87 g Density = `m/((m_2-m_1))=87/26` `=3.346 "g/cm"^3 = 3.346 xx 1000 "kg/m"^3` `=3346 "kg/m"^3`

Discussion

533.	Try to push a nail into a wooden plank by its head. Did you succeed? Trey now to push the nail by the pointed end (Fig.11.12). Could you do it this time? Try cutting vegetables with a blunt and a sharp knife. Which is easier? Do you get the feeling that the area over which the force is appied (for example, the pointed end of the nail) plays a role in making these tasks easier?
Answer» Answer :No, we cannot PUSH a NAIL into a WOODEN PLANK by its head.

Discussion

534.	Fill in the blanks : The minimum distance at which the eye can see objects distinctly varies with________.
Answer» ANSWER :AGE

Discussion

535.	A current carrying metallic comb is placed close to small iron filings, then the
Answer» iron filings will fly away from the comb, when switch is turned off. iron filings align in THEDIRECTION of the MAGNETIC field produced around the metallic comb. iron filings will be attracted by the comb. Both (b) and (c). Solution :As the switchis turned on,the current flows through the CIRCUIT and magnetic field will be produced around it. All iron filings will align in thedirection of a magnetic field. Butthe metallic comb will not behave like an ELECTRO magnet, and hence, the iron FILING willneither be attracted nor repelled.

Discussion

536.	I have a question. Can the reflected rays be further reflected if incident on another mirror?
Answer» Answer :Yes, the reflected RAYS can be further reflected if INCIDENT on ANOTHER mirror.

Discussion

537.	Which institution in India has developed knowhow to make quake-proof houses?
Answer» ANSWER :The central BUILDING Research Institute in ROORKEE has developed KNOWHOW to make quake-proof HOUSES.

Discussion

538.	Two bodies of differet metals A and B having an equal mass are given equal quantities of heat. Given that the molecular weight of A is greater than that of B, compare the specific heat capacities of the two metals. (Note that the rise in temperature is a measure of the increase in the average kinetic energy of the molecules.).
Answer» Solution :Specific heat capacity is the AMOUNT of heat energy absorbed by a unit mass of substance when its temperature is INCREASED through 1K. Let A and B be two substances of unit masses. Let the molecular weight of A be GREATER than the molecular weight of B `(M_(A) gt M_(B))`. As the mass of A and B are EQUAL, the number of molecules o B is greater than the number of molecules of `A(n_(B) gt n_(A))`. When equal amount of heat energy is supplied to A and B,the kinetic energy per molecule of A is greater than that of B as the number of molecules of A is less than that of 'B'. that is the rise in temperature of A is greater than the rise in temperature of 'B'. THEREFORE, B can absorb more amount of heat energy at less temperature. So the specific heat capacity decreases as the molecular.

Discussion

539.	Fill in the blanks : _____is the brightest object in the night sky.
Answer» ANSWER :MOON

Discussion

540.	In the following diagram if 'x' is a neutral point, identify the magnetic poles A and B. explain your answer.
Answer» Solution :(i) Definition of null point (II) The magnetic lines of force are DIRECTED from the north POLE to south pole of a MAGNET. Null points are obtained when two magnetic fields CANCEL each other at a point.

Discussion

541.	Explain the natural of force.
Answer» Answer :The NATURE of FORCE can be explained as :(i) When two or more force is APPLIED to an object in the same direction.(II) When two or more forces is applied to an object in the opposite direction.

Discussion

542.	Big Dipper,the Great Bear or the Saptarshi,are the names of the constellation_______
Answer» Orion Leo Major Cassiopeia Ursa Major Answer :D

Discussion

543.	The force exerted by a body on the earth is ______ the force exerted by the earth on the body.
Answer» ANSWER :EQUAL and OPPOSITE

Discussion

544.	Fill inthe blanks. A group of stars that appear to form a pattern in the sky is known as a _________
Answer» ANSWER :CONSTELLATION

Discussion

545.	The least dense among all the planets is ________
Answer» Saturn Neptune Uranus Mercury Answer :A

Discussion

546.	What did you obseve, when both of you were pushing the heavy box from opposite directions?
Answer» Answer :When both of US were PUSHING the HEAVY box from opposite directions, it moves in the direction of the PERSON who is applying greater FORCE.

Discussion

547.	If force applied on an object is in thedirection of its motion, the speed of the object________
Answer» increases decreases remains the same reduces to zero Answer :A

Discussion

548.	What is electric discharge?
Answer» ANSWER :When th enegative and the positive CHARGES meet, they PRODUCE streaks of LIGHT and SOUND.

Discussion

549.	Which of the following friction is highest?'
Answer» sliding static rolling drag Answer :B

Discussion

550.	What would be the time period of a seconds pendulum constructed on the earth if it is taken to the surface of the moon. The acceleration due to gravity on the surface of the moon is 1//6g_("earth")
Answer» Solution :(i) Find the length and time PERIOD of a seconds PENDULUM on the surface of the earth. Then, the formula for time period (T) is given by, `T = 2PI SQRT((l)/(g))` Take the time of seconds pendulum as `'T_(E)' and 'T_(M)'` on the surface of the earth and the earth and the moon, respectively. Take the values of acceleration due to gravity on the surface of the earth and the moon as `g_(E)' and 'g_(M)'` respectively. Given that `g_(E) = 1//6 g_(M)` Now, `T_(E) = 2pi sqrt((l)/(g_(E))) and T_(M)` `= 2pi sqrt((l)/(g_(M)))` Take, `T_(E) = 2s` Substitute the value of (1) in (2) and find the value of `T_(M)`. (ii) `4.9s`

Discussion

Explore topic-wise InterviewSolutions in .

Fill in the blanks- with suitable words. Time taken by an object to complete one oscillation is called ____________ .

What is the distance of the Sun from the Earth?

A car changes its speed from 20 km h^(-1) to 50 km h^(-1). This is possible only if ______ is applied on the car.

The transverse waves can propagate through

Fill in the blanks : Most liquids that conduct electricity are solutions of___,___ and ___.

A machine does 392 J of work in 4 seconds. What is the power of the machine?

To protect buildings fromlightning , a good conductor of electricity like a copper rod, is used.

Describe Barometer

The force involved in falling of an apple from a tree is known as _____

A chargedthermocol ball is suspended by means of anylon thread.When a neutral bodyis brought nearer to it the thermocol ball is first attracted by it and then flies away from it. Explain by giving the reason.

All mechanical forces are contact forces.

If the distance between two successive compressions of a sound wave is 16 cm, then the distance between a compression and the next rarefactions is ______

An air bubble rises up in water because,

What is night blindness?

Find out if there is an organisation in your area which provides relief to those suffering from natural disaster. Enquir. Enquire about the type of help they render to the victims of earthquakes. Prepare a brief report on the problems of the earth victims.

In an electric generator, the voltage induced across the terminals of the copper coil when it rotates in the magnetic field is

The north pole of a magnet is brought near a stationary negatively charged conductor. Will the pole experience any force?

Choose the correct option(Multiple choice questions): ___is deposited on the positive electrode when current is passed through water.

The distance between the 1st crest and the 3^(rd) crest in a transverse wavve is 10 m. Find its wavelength

Which among the following statement is/are correct?

When the mercury thread rises to 3/4th of the distance between the two fixed points, what is the temperature indicated by the Fahrenheit scale?

What causes the rectangularcoil in a D.C. motor to rotate? Explain.

Black surface is a

What are the advantages and disadvantages of using charcoal as a fuel as compared to wood ?

Which of the following substance is repelled by strong magnet ?

When your teacher is writing with chalk on the blackboard, its rough surface rubs off some chalk particies with stick to-the blackboard. Could ithappen if there were no friction between the chalk and the board?

Fill in the blanks : ________controls the amount of light entering into the eye.

A bird is sitting on the floor of a wire cage and the cage is in the hand of a boy . The bird starts flying in the cage . Will the boy experience any change in the weight of the cage ?

Magnetic lines of force due to a straight conductor carrying current are

A stone is immersed in a Eureka can. The mass of the empty beaker into which water overflowed was 30 g and the mass of the beaker with the water from the Eureka can is 56 g. If the mass of the stone is 87 g. What is the density of the stone?

Fill in the blanks : The minimum distance at which the eye can see objects distinctly varies with________.

A current carrying metallic comb is placed close to small iron filings, then the

I have a question. Can the reflected rays be further reflected if incident on another mirror?

Which institution in India has developed knowhow to make quake-proof houses?

Fill in the blanks : _____is the brightest object in the night sky.

In the following diagram if 'x' is a neutral point, identify the magnetic poles A and B. explain your answer.

Explain the natural of force.

Big Dipper,the Great Bear or the Saptarshi,are the names of the constellation_______

The force exerted by a body on the earth is ______ the force exerted by the earth on the body.

Fill inthe blanks. A group of stars that appear to form a pattern in the sky is known as a _________

The least dense among all the planets is ________

What did you obseve, when both of you were pushing the heavy box from opposite directions?

If force applied on an object is in thedirection of its motion, the speed of the object________

What is electric discharge?

Which of the following friction is highest?'

What would be the time period of a seconds pendulum constructed on the earth if it is taken to the surface of the moon. The acceleration due to gravity on the surface of the moon is 1//6g_("earth")

Fill in the blanks : Most liquids that conduct electricity are solutions of_,_ and ___.