885 + Interview Questions in Physics in Class 8 Page 2 InterviewSolution

51.	What are the safety rules to be followed when earthquakes strikes?
Answer» ANSWER :At home.Outdoors.

Discussion

52.	The density of sand is 1500 "kg/m"^3. What is the mass of 10m^3 of sand ?
Answer» ANSWER :15000 KG

Discussion

53.	SI unitof electric charge is :
Answer» ampere volt joule coulomb Answer :D

Discussion

54.	Fill in the blanks in the following statement. A charged body _______ an uncharged body towards it.
Answer» ANSWER :ATTRACTS

Discussion

55.	A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammerig affect the piece of iron?
Answer» ANSWER :When a blacksmith hammers a hot iron while making a tool, the MUSCULAR FORCE APPLIED by the blacksmith due to hammering GIVES the desire shape to the piece of iron.

Discussion

56.	Calculate the pressure in the following cases : i. On a surface with area 10 "cm"^2 if a force of 1200 N is acting normally on it. ii. On the same area (10 "cm"^2) if the normal force is increased to 2000 N.
Answer» SOLUTION :FORCE (F)=1200 N , Area (A) = 10 `cm^2` `=10 xx 10^(-4) m^2 = 10^(-3) m^2` Pressure (P)=F/A= `1200N//10^(-3) m^2` `=1.2xx10^6 N//m^2 =1.2xx10^6` Pa ii. Force (F)=2000 N , Area (A) =10 `cm^2` `=10 xx 10^(-4) m^2 = 10^(-3) m^2` Pressure (P)=F/A=`2000 N//10^(-3) m^2` `=2xx10^6 N//m^2 = 2xx10^6` Pa Therefore, we NOTICE that on the same area, pressure increases as the force increases.

Discussion

57.	Define the following: Point of incidence
Answer» Answer :POINT of incidence: Point of incidence is the point on the reflecting surface ATWHICH the INCIDENT RAY falls.

Discussion

58.	Take a rubber band. put it around the longer side of a pencil box. Insert two pencils between the box and the stretched rubber . Now,pluck the rubber band somewhere in the middle . Do you hear any sound? Does the band vibrate?
Answer» Answer :Yes, we HEAR a sound when we PLUCK the stretched rubber band SOMEWHERE in the MIDDLE. Yes , the rubber band VIBRATES.

Discussion

59.	During electrification by friction
Answer» protonsare TRANSFERRED from one body to ANOTHER body. neutrons aretransferred from one body to another body. None of the above Answer :C

Discussion

60.	Touch the end of the paper clip gently with hand and you will find a change in the foil strips. They come back to their original state. Repeat charging of foil strips and touching the paper clip. Everytime you will find that the foil strips collapse as soon as you touch the paper clip with hand. Why does it happen?
Answer» Answer :When we touch the paper CLIP with HAND, the foil STRIPS cllapse because the charge travelling from the charged refill to the foil through the paper clip GETS TRANSFERRED to the earth through our body.

Discussion

61.	When the amplitude of vibration is large, the sound produced will be _____________.
Answer» feeble shrill loud low-pitched Answer :C

Discussion

62.	A body is immersed in a liquid of relative density 2.6. It is found that the weight of the body in the liquid is two-thirds of its weight in air. Calculate the density of the body ?
Answer» Solution :Let `RHO` be the density of the body and `V_(1)` its volume, then according to Archimedes principle `V_(1)rho g-V_(1)rho_(1)g=(2)/(3)V_(1)rhog` `(rho_(1)`=density of the liquid) `THEREFORE V_(1)rho g-v_(1)rhog-(2)/(3)V_(1)rho g` `implies rho=3rho_(1)=3xx2.6xx10^(3) kg m^(-3)` `=7.8xx103 kg m^(-3)` Density of the body is `7.8xx103 kg m^(-3)`

Discussion

63.	A rubber ball of mass 100 g and radius 5 cm is submerged in water to a depth of 1 m and released. To what height will the ball jump up above the surface of water ? (Take g= 10 m s^(-2))
Answer» Solution :LET the rubber ball reach to a height 'h' above the surface of WATER. When the ball is taken to a depth of 1 m below the water surface, the GRAVITATIONAL potential energy decreases by an amount equal to MGH `=10^(-1)xx10xx1= 1 J` The work DONE against the buoyant force is, W =buoyant force x displacement `V rho g xx h =(4)/(3)pi r^(3) rho g xx h` Where `rho` is the density of water. Substituting the values, `W=(4)/(3)xx(22)/(7)(5xx10^(-2))^(3)xx1000xx10` 5.24 J (app) Total energy E below the water surface is given by subtracting equation (1) from (2) `therefore E=5.24-1` =4.24 J The 'E' is the potential energy of the ball above the water surface `therefore E=mgh =0.1xx10xxh` Equating the above with equation (3), we get `=0.1xx10xxh=4.24` h=4.24 m `therefore` The height reached by the ball above the water surface is 4.24 m

Discussion

64.	Rahul pushed a toy car and it moved a distance of 5 m. If the work done by Rahul is 1500 J, how much force did he apply through the push?
Answer» SOLUTION :Work done = 1500 J DISTANCE = 5 m Force applied = `"Work done"/"Distance"= 1500/5` =300 N

Discussion

65.	Otto von Guericke conducted an experiment to measure the strength of_______.
Answer» GRAVITATIONAL force magnetic force atmospheric pressure horses Answer :C

Discussion

66.	Find the initial velocity and acceleration of a body if the distance traveled by that body in nth second is (5.69+0.008n)m
Answer» Solution : (i) Arranging the given equation in the fomr of `S_(n)=u+(a)/(2)(2n-1)` to FIND the u and a (II) `6 m s^(-1), 0.08 m s^(-2)`

Discussion

67.	Fill in the blanks- with suitable words. The unit of frequency is ____________ .
Answer»

Discussion

68.	Can we differentiate sounds on the basis of their amplitudes and frequencies?
Answer» Answer :Yes, we can DIFFERENTIATE SOUNDS on the basis of their AMPLITUDES and FREQUENCIES.

Discussion

69.	Fill in the blanks : When a glass rod is rubbed with silk, it acquires a _______ charge.
Answer» ANSWER :POSITIVE

Discussion

70.	Given that the ratio of specific heat capacity of alcohol to that of water is 13:25, which of the following statements is true? A: When temperature is raised through 1^(@)C the heat energy absorbed by 2 kg of alcohol is less than the heat energy absorbed by 1 kg of water. B: heat capacity of 2 kg alcohol is more than the heat capacity of 1 kg water,
Answer» A is TRUE and B is FALSE. A and B are true A is false and B is true. A and B are false. Answer :C

Discussion

71.	Let us consider some more examples. In a game of vollyball, players often push the moving ball to their team mates to make a winning move. Sometimes the ball is returned to the other side of the court bypushing or smashing it. In cricket, a batsman plays his or her shot by applying a force on the ball with the bat. Is there any change in the direction of motion of the ball in these ases? In all these examples, the speed and the direction of the moving ball change due to the application of a force. Can you give a few more examples of this kind?
Answer» Answer :YES. The direction of motion of the BALL changes in all of the above MENTIONED CASES.

Discussion

72.	An empty beaker weighs 100 g. A volume of 75 mL of salt solution is taken and weighed. It is found to be 190 g. What is the density of the salt solution in "g/cm"^3 and also in "kg/m"^3?
Answer» ANSWER :`1.2 "g/cm"^3 ; 1200 "kg/m"^3`

Discussion

73.	Suppose the outer surface of the tumbler is greasy, or has a film of cooking oil on it, would it become easier or more difficult to hold it?
Answer» Answer :If the outer SURFACE of the tumbler is greasy,or has a film of COOKING oil on it, it would become more difficult to HOLD it.

Discussion

74.	The process suitablefor charging a glass rod is
Answer» CONDUCTION. induction. RUBBING against a suitable SUBSTANCE. All of the above Solution :The process suitable forcharginga GLASS rod is by FRICTION,meansby rubbingagainst a suitable substance.

Discussion

75.	The centre of gravity of a boomerang is always situated
Answer» INSIDE the MATERIAL of the body outside the material of the body at ONE of its ends None of the above Answer :B

Discussion

76.	A device used to detect whether an object is charged or not is called a_______
Answer» kaleidoscope stethosope electroscope microscope Answer :C

Discussion

77.	What do you mean by contact force?
Answer» Answer :Force which can be excerted only when OBJECTS come into CONTACT with each other is CALLED contact force.

Discussion

78.	Which of the following can be reused after charging?
Answer» DRY CELL Leclanche cell VOLTAIC cell LEAD ACID cell Answer :D

Discussion

79.	An object of weight 500 kg_(wt) is lifted by using a hydraulic press. The radii of the cross sections of the pump piston and press piston are 10 cm and 20 cm, respectively. Calculate the effort required to lift the object. Calculate the displacement of the load if the effort is moved through a distance of 20 cm.
Answer» Solution :(i)` ("LOAD")/("EFFORT")=(("radius of the lift pistion")^(2))/(("radius of the press PISTON")^(2))` Work done on the load= Work done by the effort. (ii) 5 CM.

Discussion

80.	The point beyond which a magnet cannnot be magnetised any further is called_____.
Answer» ANSWER :SATURATION

Discussion

81.	In human beings, sound is produced when the_________ vibrate.
Answer» pharynx larynx wind pipe vocal cords Answer :D

Discussion

82.	Define earthing.
Answer» Answer :Earthing is the PROCESS through which a charged BODY DISCHARGES its charge to the earth.

Discussion

83.	Fill in the blanks in the following statement. To draw water from a well we have to _______ at the rope.
Answer» ANSWER :PULL

Discussion

84.	A: At high altitude regions the cooking of food becomes difficult B: Water boils at lower temperature when the presure is low.
Answer» Both A and B are wrong. A and B are CORRECT and B is not the correct EXPLANATION of A. A and B are correct and B is the correct explanation of A. A is correct but B is wrong. Answer :C

Discussion

85.	What is crust?
Answer» Answer :CRUST is the UPPERMOST layer of the EARTH which is FRAGMENTED.

Discussion

86.	A spring made of copper is moved towards a stationary bar magnet. What are the changes observed in the spring when (1) the to ends of the spring are connected. (2) the two ends of the spring are not connected.
Answer» SOLUTION :(i) Requirement for current to flow. (II) DIFFERENCE between geographical AXIS and geographical meridian. (iii) Change in the length of the spring. (iv) Pole STRENGTH decreases when the area of cross-section of the bar magnet is reduced and the

Discussion

87.	Can you push or lift a book lying on a table without touching it? Can you lift a bucket of water without holding it?
Answer» ANSWER :No, we cannot push or lift a book lying on a table WITHOUT touching it.

Discussion

88.	The distance between a compression and the next rarefaction of a sound wave is 12.5 cm. If the sound waves can travel 750 m in 3s, then find the number of waves produced in one second
Answer» Solution :(i) Time taken to PRODUCE ONE WAVE = (WAVELENGTH) (distance covered in one second) (ii) 1000

Discussion

89.	A magnet and a coil are taken. In which of the following cases, emf is induced in the coil ?
Answer» magnet is MOVING, coil is at rest. magnet is at rest and the coil is moving. both magnetic and coil are moving with equal velocities. magnet is moving with GREATER velocity than that of coil. Solution :(i) Relative motion between coil and the magnet. (ii) Varying magnetic field - INDUCED emf.

Discussion

90.	What is a blind spot?
Answer» Answer :The spot at the JUNCTION of optic nerves and retina in the EYE where sensory cells are absent and no vision is possible is CALLED the BLIND spot.

Discussion

91.	The advantage of alcohol is thermometric liquid is due to its
Answer» low boiling POINT low freezing point. high vapour pressure. All the above Solution :Because of its low freezing point `(-130^(@)C)`, it CFAN be USED to record very low TEMPERATURE.

Discussion

92.	What is fluid friction?
Answer» Answer :The force of friction EXERTED when an object MOVES in air or water or other gases or LIQUIDS is called FLUID friction. It is also known as drag.

Discussion

93.	Which is false aboutelectrolysis ?
Answer» Most commonlyoccurringchemical reactionin electrolysisis the 'chemical decomposition reaction'. When an iron rod is to be electroplated withchromium, chromiumelectrode is usedas ANODE and iron rod is used as cathode. Duringelectrolysis of water,`H_(2)` accumulates atcathode and `O_(2)`accumulates at anode. When electrolysis is used inmetallurgicalapplications, theconcentration of electrolyte changes. Solution :There will be no change in the concentration of electrolyte PARTICULARLY when electrolysisis used in METALLURGICAL applications.

Discussion

94.	Solve the following riddle and try to make similar riddles yourself : My first is in VAN but not in PAN My second is in EARTH and also in HEAVEN My third is in ONE and not in TWO My fourth is in BUN and also in FUN My last is in STAR but not in RADAR I am a planet that moves round the sun.
Answer» ANSWER :VENUS

Discussion

95.	State whether the following statements are true or false : The mass of Jupiter is about 318 times than that of the Earth.
Answer» ANSWER :1

Discussion

96.	Name two objects other than planets which are members of the Solar System.
Answer» ANSWER :Two objects, other than planets, which are MEMBERS of the SOLAR SYSTEM are asteroids and COMETS

Discussion

97.	A box of books weighing 80 kg is on a table 75 cm high. What is its potential energy relative to the floor?
Answer» SOLUTION :m=80 KG , h=75 CM or 0.75 m `g=10 m//s^2` PE=mgh= 80 x 10 x 0.75 = 800 x 0.75 = 600 J

Discussion

98.	Bituminous coal is the finest quality of coal. True/ False
Answer» ANSWER :F

Discussion

99.	What do you mean by musical sound or music?
Answer» Answer :Sound produced by musical instruments which is PLEASING to our EARS is CALLED musical sound or music. For example, sound produced by guitar, SITAR, HARMONIUM, etc. is musical sound or music.

Discussion

100.	State whether the following statements are true or false : Insufficient light causes eyestrain and headaches.
Answer» ANSWER :1

Discussion

Explore topic-wise InterviewSolutions in .

What are the safety rules to be followed when earthquakes strikes?

The density of sand is 1500 "kg/m"^3. What is the mass of 10m^3 of sand ?

SI unitof electric charge is :

Fill in the blanks in the following statement. A charged body _______ an uncharged body towards it.

A blacksmith hammers a hot piece of iron while making a tool. How does the force due to hammerig affect the piece of iron?

Calculate the pressure in the following cases : i. On a surface with area 10 "cm"^2 if a force of 1200 N is acting normally on it. ii. On the same area (10 "cm"^2) if the normal force is increased to 2000 N.

Define the following: Point of incidence

Take a rubber band. put it around the longer side of a pencil box. Insert two pencils between the box and the stretched rubber . Now,pluck the rubber band somewhere in the middle . Do you hear any sound? Does the band vibrate?

During electrification by friction

When the amplitude of vibration is large, the sound produced will be _____________.

A body is immersed in a liquid of relative density 2.6. It is found that the weight of the body in the liquid is two-thirds of its weight in air. Calculate the density of the body ?

A rubber ball of mass 100 g and radius 5 cm is submerged in water to a depth of 1 m and released. To what height will the ball jump up above the surface of water ? (Take g= 10 m s^(-2))

Rahul pushed a toy car and it moved a distance of 5 m. If the work done by Rahul is 1500 J, how much force did he apply through the push?

Otto von Guericke conducted an experiment to measure the strength of_______.

Find the initial velocity and acceleration of a body if the distance traveled by that body in nth second is (5.69+0.008n)m

Fill in the blanks- with suitable words. The unit of frequency is ____________ .

Can we differentiate sounds on the basis of their amplitudes and frequencies?

Fill in the blanks : When a glass rod is rubbed with silk, it acquires a _______ charge.

An empty beaker weighs 100 g. A volume of 75 mL of salt solution is taken and weighed. It is found to be 190 g. What is the density of the salt solution in "g/cm"^3 and also in "kg/m"^3?

Suppose the outer surface of the tumbler is greasy, or has a film of cooking oil on it, would it become easier or more difficult to hold it?

The process suitablefor charging a glass rod is

The centre of gravity of a boomerang is always situated

A device used to detect whether an object is charged or not is called a_______

What do you mean by contact force?

Which of the following can be reused after charging?

The point beyond which a magnet cannnot be magnetised any further is called_____.

In human beings, sound is produced when the_________ vibrate.

Define earthing.

Fill in the blanks in the following statement. To draw water from a well we have to _______ at the rope.

A: At high altitude regions the cooking of food becomes difficult B: Water boils at lower temperature when the presure is low.

What is crust?

A spring made of copper is moved towards a stationary bar magnet. What are the changes observed in the spring when (1) the to ends of the spring are connected. (2) the two ends of the spring are not connected.

Can you push or lift a book lying on a table without touching it? Can you lift a bucket of water without holding it?

The distance between a compression and the next rarefaction of a sound wave is 12.5 cm. If the sound waves can travel 750 m in 3s, then find the number of waves produced in one second

A magnet and a coil are taken. In which of the following cases, emf is induced in the coil ?

What is a blind spot?

The advantage of alcohol is thermometric liquid is due to its

What is fluid friction?

Which is false aboutelectrolysis ?

Solve the following riddle and try to make similar riddles yourself : My first is in VAN but not in PAN My second is in EARTH and also in HEAVEN My third is in ONE and not in TWO My fourth is in BUN and also in FUN My last is in STAR but not in RADAR I am a planet that moves round the sun.

State whether the following statements are true or false : The mass of Jupiter is about 318 times than that of the Earth.

Name two objects other than planets which are members of the Solar System.

A box of books weighing 80 kg is on a table 75 cm high. What is its potential energy relative to the floor?

Bituminous coal is the finest quality of coal. True/ False

What do you mean by musical sound or music?

State whether the following statements are true or false : Insufficient light causes eyestrain and headaches.