885 + Interview Questions in Physics in Class 8 Page 12 InterviewSolution

551.	Fill in the blanks: The circuit of the tester is complete when the liquid between the two ends of the tester allow ___ to pass.
Answer» ANSWER :ELECTRIC CURRENT

Discussion

552.	Calculate the pressure produced by a force of 800 N acting on an area of 2 m^2
Answer» Solution :Force (F) = 800 N, Area (A) = `2m^2` PRESSURE (P)=F/A = `800 N//2m^2` `=400 N//m^2`=400 Pa

Discussion

553.	Among the following statements. A: A simple pendulum of a given length and at a given place has a constant time period B: A simple pendulum with constant time period can be used as a time measuring device
Answer» Only A is true Only B is true both A and B are true Both A and B are false Answer :B

Discussion

554.	Volt is the unit of__________
Answer» emf current resistance charge Answer :A

Discussion

555.	Choose the correct option (Multiple choice questions) : Lack of ________in food stuff is responsible for many eye troubles.
Answer» VITAMIN A Vitamin B Vitamin C Vitamin D Answer :A

Discussion

556.	Fill in the blanks: When electric current is passed through the copper sulphate solution, itdissociates into ___ and___ .
Answer» ANSWER :COPPER,SULPHATE

Discussion

557.	What are insulators?
Answer» ANSWER :Insulators are MATERIALS which do not allow electric current,to pass THROUGHTHEM. FOREXAMPLE, rubber, wood, plastic, distilled WATER, etc.

Discussion

558.	State whether the following statements are true orfalse : Ballbearings are used between hubs and the axles of celling fans and bicycles to reduce sliding friction.
Answer» ANSWER :1

Discussion

559.	Why do stars appear to move from east to west?
Answer» ANSWER :Stars appear to move from EAST to west because the Earth rotates on its own axis from west to east.

Discussion

560.	A test tube of uniform cross-section is floated vertically in a liquid 'A' (density rho A) upto a mark on it when it is filled with 'x' ml of a liquid 'B' (density rho B). To make the test tube float in liquid B upto the same mark it is filled with y ml of the liquid A. Find the mass of the test tube.
Answer» Solution :(i) What is law of floatation ? Is mass of the TEST TUBE (float)changed, when it is immersed in DIFFERENT liquids ? Then, can we SAY that it is a constant immersion hydrometer ? Assume the mass of the testtube =M. When immersed in liquid 'A', the float is filled with 'x' ml of liquid B. Then, find the weight of the float. Is the volume of liquid 'B' in the float =x ml. Then, weight of the liquid =vdg. Now, the weight of the float `=mg +x rho B G` Similarly, find the weight of the float when immersed in liquid 'B'. Is the weight of the float `= mg+y rho A g` But, weight of the float = weight of the displaced liquid. The volume of the displaced liquids (both A and B) are equal. Then get the volume of displaced liquids from above two cases in form of equations and equate them. From this, obtain the mass of the test tube. (ii) 51680 Pa

Discussion

561.	When you inflate a ballon, why do you have to close its mouth?
Answer» ANSWER :When we inflate a balloon we have to CLOSE its mouth, so that the AIR does not come out of the BALLOONS and deflate it.

Discussion

562.	Alida runs her car on dry marble floor, wet marble floor, newspaper and towel spreadon the floor. The force of friction acting on the car on different surfaces in increasing order will be
Answer» WET marble FLOOR, DRY marble floor, newspaper and towel. newspaper, towel, dry marble floor, wet marble floor. towel, newspaper, dry marble floor, wet marble floor. wet marble floor, dry marble floor, towel, newspaper. Answer :A

Discussion

563.	When a plastic comb is rubbed with dry hair, it is called ______.
Answer» CHARGED objects negatively charged objects positively charged objects neutral objects Answer :A

Discussion

564.	Choose the correct option(Multiple choice questions): Magnetic needle will not show defiection for ___.
Answer» TAP water distilled water lemon juice vegetable juice Answer :B

Discussion

565.	Fill inthe blanks. A celestial body that revolves around a planet is known as___________
Answer» ANSWER :SATELLITE

Discussion

566.	Which of the following properties of a magnet is/are used in navigation ?
Answer» PAIR property Laws of MAGNETIC poles Directional property Attractive property Answer :C

Discussion

567.	Define angle of declination.
Answer» `90^(@)` at the poles `0^(@)` at the equator variable none of the above Solution :The angle of DECLINATION changes from PLACE to place even along MAGNETIC equator.

Discussion

568.	If the refractive index of alcohol is 1.36, what will be the speed of light in it?
Answer» ANSWER :`2.2xx10^8` m/s

Discussion

569.	What are seismic zones?
Answer» Answer :The boundaries of the PLATES, which are CONSIDERED to be weak zones, are most susceptible to EARTHQUAKES. These weak zones are CALLED seismic zones or fault zones.

Discussion

570.	Fill in the blanks : No surface is __________
Answer» ANSWER :PERFECTLY SMOOTH

Discussion

571.	If the work done in pushing a trolley by applying a force of 850 N is 1275 J. calculate the distance moved by the trolley.
Answer» Solution :WORK DONE = 1275 J FORCE = 850 N Distance moved = `"Work done"/"Force"` `= 1275/850`=1.5 m

Discussion

572.	Can any life exist on the moon?
Answer» ANSWER :No,life cannot EXIST on the moon becauseit has no ATMOSPHERE and WATER

Discussion

573.	How is the hair set well when oil is applied to it ?
Answer» Solution :(i) Surface TENSION (II) `0.6 g cm^(-5)`

Discussion

574.	It is a convention to call the charge acquired by a glass rod when it is rubbed with silk as positive. The other kind of charge is said to be negative. It is observed that when a charged glass rod is brought near a charged plastic straw rubbed with polythene, there is attraction between the two. What doi you think would be the kind of charge on the plastic straw?
Answer» ANSWER :The PLASTIC STRAW ACQUIRED a negative charge.

Discussion

575.	A stone has a mass of 108.5 g. When the stone is totally immersed in water contained in a measuring cylinder, it displaces water from "50 cm"^3 to 93 "cm"^3. Find the density of the stone.
Answer» SOLUTION :Mass of the STONE =108.5 g Volume of stone = 93-50 =43 `"cm"^3` DENSITY = mass/volume = 2.5 `"g/cm"^3`

Discussion

576.	Which of the following represents the smallest temperature change?
Answer» `1^(@)C` `1^(@)F` `1K` Both a and B Answer :B

Discussion

577.	Fill in the blanks: When the free ends of the tester do not touch each other, there is an __ between them.
Answer» ANSWER :AIR GAP

Discussion

578.	Sound travels in rocks in the form of both longitudinal and transverse waves, but in air, sound travels only in the form of longitudinal waves'. Explain
Answer» Solution :Longitudinal waves are POSSIBLE in those media which resist change in volume TRANSVERSE waves are possible in those media which resist change in SHAPE.

Discussion

579.	What is one hertz?
Answer» Answer :The FREQUENCY of one oscillation in 1 sec is CALLED one hertz.

Discussion

580.	State whether the following statements are true or false : White light consists of seven colours.
Answer» ANSWER :1

Discussion

581.	No-liquid barometer is
Answer» a MERCURY barometer an ANEROID barometer a Fortin's barometer Torricelli's barometer Solution :N//A

Discussion

582.	What purpose does the brala,pads in the brake system of bicycles and other vehicles serve?
Answer» ANSWER :Brake-pads in the brake system of bicycles and other VEHICLES HELP in INCREASING friction to stop them.

Discussion

583.	What is an earthquake? What happens when it occurs? What can we do to minimise its effects?
Answer» ANSWER :The sudden tremling or shaking of the earth for a very short period of TIME is called EARTHQUAKE. It is cause by disturbances in the lower LEVEL of the earth's crust.

Discussion

584.	Have you ever made a toy telephone? Can you say that sound can travel through strings?
Answer» ANSWER :YES ,SOUND can TRAVEL through STRINGS.

Discussion

585.	The average kinetic energy of the molecules of substance_________during the process of melting.
Answer» SOLUTION :REMAINS same

Discussion

586.	At the mount of the tap area of cross-section is 2.0cm^(2) and the speed of water is 3m//s. The area of cross-section of the water column 80 cm below the tap is (use g=10m//s^(2))
Answer» SOLUTION :(i) `(d_(0))/(d_(W))=("voulume of liquid displaced")/("Volulme of the OBJECT")` `=("RISE in LEVEL") xx (A_(c )-A_(0))/(A_(0)xx(1_(0)))` (ii) `0.6 g cm^(-s)`

Discussion

587.	Mark the following statements as true (T) or false (F) . INSAT is an artificial satellite.
Answer» ANSWER :T

Discussion

588.	In Fig. A, can you tell why there is no refraction at C.
Answer» SOLUTION :NORMAL. of C is BC itself . HENCE, `anglei=0`

Discussion

589.	Fill in the blanks : ______ are used for telecommunication and remote sensing.
Answer» ANSWER :ARTIFICIAL SATELLITES

Discussion

590.	A body moving along a straight path covers one-third of a distace with a velocity of 5 Kmph and the rest of the path with a velocity of 20 Kmph. Find the average velocity of the body
Answer» Solution :Let the length of the PATH be 'x' the time taken by the body to reacyh (1/3) RD of he distance be `'t_(1)'` and the time taken by body to cover REST of the distancebe `'y_(2)'` 5Kpmph `=((x//3))/(t_(1)) , 20 Kmph =((2x//3))/(t_(2))` `rArr t_(1)=(x)/(15)` hours, `t_(2)=(x)/(30)` hours Average velocity = `("TOTAL displacement")/("Total time taken") =(x)/(t_(1)+t_(2))=10Kmph`

Discussion

591.	Fill in the blanks : Electrical charge can be transferred from a charged body to another object through a ______.
Answer» ANSWER :METAL CONDUCTOR.

Discussion

592.	A solar panel containing 1500 solar cell each of surfaces area 5 cm^(2) arranged in parallel combinations, is used to supply electrical energy for domestic needs. The efficiency of a solar cell is 35% and 600 J of energy is incident on one square metre area in one second, find the electrical energy generated in one hour.
Answer» SOLUTION :(i) Efficiency =`("ENERGY UTILIZED")/("Energy supplied ")` (II) 567 Kj

Discussion

593.	A Bullet Train in Japan starting from rest accelerates uniformly at 0.5m s^(-2) for 2 minutes. It then maintains uniform speed for 20 minutes and then retards uniformly at the rate of 0.25 m s^(-1) and comes to rest. Calculate the average speed of the train
Answer» SOLUTION : `53 m s^(-1)`

Discussion

594.	Fill inthe blanks. The planet which appears reddish in colour is ______
Answer» ANSWER :MARS

Discussion

595.	Statement-A : For nuclear fusion to take place a very high temperature is required Statement-B hydrogen bomb is based on a nuclear fusion reaction.
Answer» Both STATEMENTS A and B are TRUE. STATEMENT A is true. Statement (B) is FALSE. Statement A is false, statement B is true. Both statement A and B are false. Answer :A

Discussion

596.	Explain why porters place a round piece of cloth on their heads when they have to carry heavy load.
Answer» Answer :Porters place a ROUND piece of CLOTH on their heads when they have to carry heavy LOAD because by doing so they increasee the AREA of contact which REDUCES the pressure.

Discussion

597.	What do you mean by force of friction?
Answer» ANSWER :The force OPPOSING relative motion between the two SURFACES in contact is called the force of FRICTION.

Discussion

598.	Solar cell is a device which converts light energy into electric energy.
Answer» ANSWER :T

Discussion

599.	In a D.C. motor, concave cylindrical magnets produce a____magnetic field.
Answer» ANSWER :RADIAL

Discussion

600.	When two marbles, collide, their total momentum before collision is equal to
Answer» the DIFFERENCE in their momentum after collision the average of their momentum after collision the SQUARE of the SUM of their momentum after collision their total momentum after collision. Answer :D

Discussion

Explore topic-wise InterviewSolutions in .

Fill in the blanks: The circuit of the tester is complete when the liquid between the two ends of the tester allow ___ to pass.

Calculate the pressure produced by a force of 800 N acting on an area of 2 m^2

Among the following statements. A: A simple pendulum of a given length and at a given place has a constant time period B: A simple pendulum with constant time period can be used as a time measuring device

Volt is the unit of__________

Choose the correct option (Multiple choice questions) : Lack of ________in food stuff is responsible for many eye troubles.

Fill in the blanks: When electric current is passed through the copper sulphate solution, itdissociates into ___ and___ .

What are insulators?

State whether the following statements are true orfalse : Ballbearings are used between hubs and the axles of celling fans and bicycles to reduce sliding friction.

Why do stars appear to move from east to west?

When you inflate a ballon, why do you have to close its mouth?

Alida runs her car on dry marble floor, wet marble floor, newspaper and towel spreadon the floor. The force of friction acting on the car on different surfaces in increasing order will be

When a plastic comb is rubbed with dry hair, it is called ______.

Choose the correct option(Multiple choice questions): Magnetic needle will not show defiection for ___.

Fill inthe blanks. A celestial body that revolves around a planet is known as___________

Which of the following properties of a magnet is/are used in navigation ?

Define angle of declination.

If the refractive index of alcohol is 1.36, what will be the speed of light in it?

What are seismic zones?

Fill in the blanks : No surface is __________

If the work done in pushing a trolley by applying a force of 850 N is 1275 J. calculate the distance moved by the trolley.

Can any life exist on the moon?

How is the hair set well when oil is applied to it ?

A stone has a mass of 108.5 g. When the stone is totally immersed in water contained in a measuring cylinder, it displaces water from "50 cm"^3 to 93 "cm"^3. Find the density of the stone.

Which of the following represents the smallest temperature change?

Fill in the blanks: When the free ends of the tester do not touch each other, there is an __ between them.

Sound travels in rocks in the form of both longitudinal and transverse waves, but in air, sound travels only in the form of longitudinal waves'. Explain

What is one hertz?

State whether the following statements are true or false : White light consists of seven colours.

No-liquid barometer is

What purpose does the brala,pads in the brake system of bicycles and other vehicles serve?

What is an earthquake? What happens when it occurs? What can we do to minimise its effects?

Have you ever made a toy telephone? Can you say that sound can travel through strings?

The average kinetic energy of the molecules of substance_________during the process of melting.

At the mount of the tap area of cross-section is 2.0cm^(2) and the speed of water is 3m//s. The area of cross-section of the water column 80 cm below the tap is (use g=10m//s^(2))

Mark the following statements as true (T) or false (F) . INSAT is an artificial satellite.

In Fig. A, can you tell why there is no refraction at C.

Fill in the blanks : ______ are used for telecommunication and remote sensing.

A body moving along a straight path covers one-third of a distace with a velocity of 5 Kmph and the rest of the path with a velocity of 20 Kmph. Find the average velocity of the body

Fill in the blanks : Electrical charge can be transferred from a charged body to another object through a ______.

A Bullet Train in Japan starting from rest accelerates uniformly at 0.5m s^(-2) for 2 minutes. It then maintains uniform speed for 20 minutes and then retards uniformly at the rate of 0.25 m s^(-1) and comes to rest. Calculate the average speed of the train

Fill inthe blanks. The planet which appears reddish in colour is ______

Statement-A : For nuclear fusion to take place a very high temperature is required Statement-B hydrogen bomb is based on a nuclear fusion reaction.

Explain why porters place a round piece of cloth on their heads when they have to carry heavy load.

What do you mean by force of friction?

Solar cell is a device which converts light energy into electric energy.

In a D.C. motor, concave cylindrical magnets produce a____magnetic field.

When two marbles, collide, their total momentum before collision is equal to

Fill in the blanks: When electric current is passed through the copper sulphate solution, itdissociates into _ and_ .