885 + Interview Questions in Physics in Class 8 Page 15 InterviewSolution

701.	A new scale of temperature called TIME is introduced. The reading on the new scale is twice the reading on the new scale is twice the reading on a celsius scale when the temperature of a certain body is 373 K. The reading on a Fahrenheit scale is found to (17/15)th the reading on TIME scale when the temperature of a body is 20^(@)C. Determine the upper fixed point and lower fixed point of the TIME scale.
Answer» Solution :LET `.^(T)` represent the temperature in TIME SCALE. 373K `=100^(@)C` `U=200.^(T)` `(20-0)/(100)=(F-32)/(180)` `(20)/(100)=(F-32)(180)` `F-32=18xx2` `F=36+32=68^(@)F` Temperature on TIME scale corresponding to `20.^(@)C` `=(68xx15)/(17)=60.^(@)C` `(68-32)/(180)=(60-L)/(200-L)` `(200-L)=300-5L` `4L=100` ltBrgt `L=25.^(@)T` `therefore` The lower fixed point and upper fixed point are `25.^(@)T` and `200.^(@)T`, repspectively.

Discussion

702.	Draw a circle of about 1m diameter on the ground.Ask one of your friends to stand at the centre of this circle.You revolve around your friend in such a manner that your face always remains towards him . Can your friend see your back?
Answer» ANSWER :No,my FRIEND canno't SEE my BACK.

Discussion

703.	Draw a circle of about 1m diameter on the ground.Ask one of your friends to stand at the centre of this circle.You revolve around your friend in such a manner that your face always remains towards him . How many rotations did you complete in one revolution? The moon revolves around the Earth in a similar manner. .
Answer» ANSWER :I COMPLETE only ONE ROTATION in one REVOLUTION.

Discussion

704.	A mirror changes the direction ofligh that falls on it, Can you tell in which direction, the light falling on a surface will be reflected?
Answer» Answer :The light RAY FALLING on a surface will be reflected in another DIRECTION after striking its surface..

Discussion

705.	Have you ever seen a game of tug-of war? In this game two teams pull at a rope in opposite directions (Fig.11.5). Members of both the teams try to pull the rope in their direction. Sometimes the rope simply does not move. Is it not similar to the situation shown in Fig.11.3(b)?
Answer» ANSWER :YES, I have seen a game of tug-of-war.Yes, it is similar to the situation WHOWN in Fig.11.3(B).

Discussion

706.	Fill in the blanks : The outer planets have large number of ___________
Answer» ANSWER :MOONS

Discussion

707.	Define the following: Angle of reflection
Answer» Answer :Angle of reftection: The angle between the reflected RAY and the normal at the point of INCIDENCE is CALLED the angle of REFLECTION.

Discussion

708.	When does a force come into play?
Answer» ANSWER :FORCE COMES into play when TWO objects interact with each other.

Discussion

709.	Fill in the blanks : The electric charges generated by rubbing are______.
Answer» ANSWER :STATIC

Discussion

710.	The iron rims are fitted to the wooden wheels of bullock carts and tongas by process of ____
Answer» SOLUTION :THERMAL EXPANSION

Discussion

711.	Do you remember lightning is an electrical discharge?
Answer» ANSWER :YES, LIGHTNING is an elkectrical DISCHARGE.

Discussion

712.	A cubic lump of cheese of area 10 "cm"^2 and weight 3 N stands on a table. Calculate the pressure exerted by it on the table?
Answer» Solution :Force (F)=3 N, AREA (A) = `10 cm^2 = 10xx10^(-4) m^2 =10^(-3) m^2` Pressure (P)=F/A=`3N//10^(-3) m^2` `=3xx10^3` PA

Discussion

713.	Suggest a method to fill water in a tank constructed at a height of 10 m from the ground by using a vacuum pump instead of an electric pump.
Answer» Solution :Construct a tank at a height of 10 m and create vacumn inside it by USING a vaccum pump. Water raises to a height of 10.34 cm due to the atmospheric PRESSURE. One END of a pipe is placed in the water at the ground. When the other end is connected to VACUM pump water raises up due to atmospheric pressure. The water can be filled in the tank.

Discussion

714.	A cuboid of dimensions 3 m xx 2m xx 1m is placed on a surface such that the face with maximum surface area is in contact. If the weight of the cuboid is 1kg_(wt), the pressure exerted by it on the surface is _____. (take g=10 m s^(-2)).
Answer» Solution :PRESSURE`=(F)/(A)=(1XX10)/(3xx2)=(10)/(6)=(5)/(3) NM^(-2)`

Discussion

715.	Which of the following has the highest calorific value ?
Answer» LPG CNG hydrogen petrol Answer :C

Discussion

716.	Can a charged body 'A' having a very small charge on it, be used to charge an uncharged body 'B' , such that the charge acquired by 'B' is many times more than that on 'A'? If so, how? Explain.
Answer» SOLUTION :Use ANOTHER body and CHARGE it by transferred to B.What happens to the charge on B and A if we repeat this process?

Discussion

717.	Find the volume of 900 g of cooking oil whose density is 0.9 "g/cm"^3. Give the answer in litres.
Answer» ANSWER :1000 `"CM"^3` = 1000 ML = 1 litre

Discussion

718.	Explain why we take short steps while walking on slippery surfaces.
Answer» Solution :Is the FRICTIONAL force LESS on SLIPPERY surfaces? How can we increase the normal reaction between the feet and the ground?

Discussion

719.	How is lightning cause?
Answer» Answer :Lightning is CAUSE when CHARGES PILE up in the CLOUD.

Discussion

720.	Fill in the blanks in the following. If you touch your________ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with________.
Answer» ANSWER :LEFT,left HAND

Discussion

721.	Name the different kinds of charge.
Answer» Answer :there are two KINDS of charge. They are :(i) POSITIVE charge and(II) NEGATIVE charge.

Discussion

722.	why earth can be considerd as a huge bar magnet.
Answer» ANSWER :T

Discussion

723.	An electric kettle of power 2 kW is used for 1 minute. Find the energy supplied by the kettle.
Answer» ANSWER :120000 J

Discussion

724.	Explain why it is not possible to magnetise an iron rod beyond a certain limit ?
Answer» SOLUTION :What happens when a diamagnetic SUBSTANCE, a PARAMAGNETIC substance and a MAGNET are placed in an external MAGNETIC field?

Discussion

725.	The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.
Answer» ANSWER :No, if it has been predicted that a THUNDERSTORM is LIKELY to occur, we should avoid using UMBRELLA.

Discussion

726.	If the stars appear to move from east to west, could it mean that the Earth, rotates from west to east?
Answer» ANSWER :YES, if the stars APPEAR to move from east to west, it MEANS that the Earth ROTATES from west to east

Discussion

727.	Fill in the blanks- with suitable words. Unwanted sound is called
Answer»

Discussion

728.	What do you mean by luminous objects? Give examples.
Answer» Answer :Luminous OBJECTS are the objects which EMIT their own light. For EXAMPLE, sun, fire, flame of a CANDLE,an electric lamp, firefly(JUGNU), etc.

Discussion

729.	The density of a given mass of a gas when 10 Pa pressure acts on it is 2 kg m^(-3). Calculate the density of the gas if the pressure is increased by 5 Pa at constant temperature.
Answer» SOLUTION :` p alpha d` at CONSTANT temperature `(P_(1))/(d_(1))=(P_(2))/(d_(2)), (10)/(2)=(15)/(d)` `5=(15)/(d)` `d=3 kg m^(-3)`

Discussion

730.	Name the largest planet of the Solar System.
Answer» ANSWER :JUPITER is the largest planet of the SOLAR System

Discussion

731.	Match the entries given in column A with appropriate ones in column B
Answer» Answer :A:d B:f C:J D:a E:g F:I G: b H :c I:e J:h

Discussion

732.	Fill in the blanks: The two wires attached to a LED are called ___.
Answer» ANSWER :LEADS

Discussion

733.	What happens if earthing is not proper in a telegraph ?
Answer» Solution :How does the ELECTRIC circuit GET closed between two PLACES in a telegraph? Will earth conduct electricity? It is POSSIBLE to send the message from one place to ANOTHER if the circuit is not closed ? Is it possible to receive message is earthing is not proper ?

Discussion

734.	An ebonite rod is rubbed with fur or wool. What type of charges do theyacquire ?
Answer» ANSWER :LOSES

Discussion

735.	What is non-contact force?
Answer» Answer :The FORCE which can be excerted between two objects without coming into CONTACT with each other is called non-contact force.

Discussion

736.	Give an example where low inertia is preferred and an example where high inertia is recommended.
Answer» SOLUTION :What is the measure of inertia? What are the ADVANTAGES and disadvantages of LOW inertia? What are the advantges and disadvantages of high inertia? Does the hammer used by a blacksmith have high inertia or low inertia? Does the hammer used by a CARPENTER have high inertia or low inertia?

Discussion

737.	Compare the sound of a baby with that of an adult. Is there any difference?
Answer» Answer :YES; there is DIFFERENCE between the sound of a BABY end that of an adult. The voice of a baby is shriller than that of an adult

Discussion

738.	How does the vocal cord affect the quality of voice?
Answer» ANSWER :The quality of voice depends on the STIFFNESS and looseness of the vocal cord. The voice DIFFERS considerably when the vocal cord is TIGHT and thin and when it is loose and THICK.

Discussion

739.	A clock has its minut hand 14 cm long. At what speed and at what velocity does the tip of the minute hand move in a half an hour duration ?
Answer» Solution : Length of the minute had of the clock=14 cm During a half an hour duration, the tip of the minute hand moves between two diameterically opption position. Thus, the distacne MOVED by the tip of the minute handis equal to halfthe circumferenc of hte circular path ALONG which the tip moves `(1)/(2) (2por)` where 'r' is thelength of the minute hand. `:.` Distance `=(1)/(2)xx2xx(22)/(7)xx14 cm=44`cm Distacemetn of the tip of the minute hand is equal to the diameter of the circular path along which the tip moves =2r `:.` Displacement `=2r =2(14) cm =28 m` The time of TRAVEL of the tip of the minute, hand, `t=30 min =30xx60s =1800s` Speed of the minute =`("Distance")/("time")` `=(44cm)/(1800s)=(11)/(450)cms^(-1)` VELOCITY fo the minute hand `=("Dispacement")/("time")` `=(28cm)/(1800s)=(7)/(450)cm s^(-1)`

Discussion

740.	Calculate the area of a body which experiences a pressure of 60 kPa by a force of 12,000 N.
Answer» ANSWER :`0.2 m^2`

Discussion

741.	The process of burning a material in theabsence of oxygen is called destructive distillation.
Answer» True False Answer :T

Discussion

742.	Arrange the following steps in proper sequence to determine the pressure exerted by a gas enclosed in a container using a manometer. (a)Connect one end of the manometer to the container filled with gas. (b)Both the limbs of the manometer are exposed to air, mercury level in both the limbs are equal due to atmospheric pressure. (c )Determine the difference in level of the mercury in both the limbs of the manometer (l). (d) If the level of the mercury in the limb connected to the container is above the mercury level in the limb exposed to air, the pressure of the gas in the container is determined as atmospheric pressure -l. (e ) If the level of the mercury in the limb connected to the container is below the mercury level in the limb exposed to air, the pressure of the gas in the container is determined as atmospheric pressure +l. (f) Note the level of the mercury in the limbs of the manometer.
Answer» a b c e F e e b a d c f b a c f d e b c d a f e Solution :(a) Initially both the limbs of manometer are exposed to air, level of mercury in both the limbs are equal due to atmospheric PRESSURE. (b) CONNECT one end of the manometer to the cylinder filled with gas. (c ) Determine the difference in the level of the mercury in both the limbs of the manometer. (d) NOTE the level of the mercury in the limbs of the manometer. (e ) If the level of the mercury in the limb connected to the container is above the mercury level in the limb exposed to air, the pressure of the gas in the container is determined as atmospheric pressure - l. (f) If the level of the mercury in the limb connected to the container is below the mercury level in the limb exposed to air, the pressure is determined as atmospheric Pressure +l.

Discussion

743.	Under what conditions air can conduct electricity?
Answer» Answer :During LIGHTING, air can ALSO CONDUCT ELECTRICITY.

Discussion

744.	Define gravitational force.
Answer» Answer :The EARTH has the POWER to attract or PULL things towards it. The force excerted by earth and all other OBJECTS in the universe to pull things towards it.

Discussion

745.	Fill in the blanks : The sense of________ is one of the most important senses.
Answer» ANSWER :SIGHT

Discussion

746.	State whether the following statements are true orfalse : Friction causes wastage of energy.
Answer» ANSWER :1

Discussion

747.	In a nuclear reactor, the energy is released by bormbarding uranium nucleaus with _______
Answer» FAST MOVING NEUTRONS slow moving `ALPHA`-particles fast moving electrons slow moving neutrons Answer :D

Discussion

748.	A gold leaf electroscope is used for
Answer» detect the PRESENCEOF chargeon a body know the NATURE of CHARGE on a charged body find the AMOUNT of charge present on a charged body Both (a) and (B) Answer :D

Discussion

749.	What is force of friction?
Answer» Answer :the FORCE excerted when the surfaces of two OBJECTS COME into CONTACT with each oter is called the force of friction.

Discussion

750.	A substance placed near a strong magnet is attracted by it, substance can be _______.
Answer» a MAGNET paramegnetic SUBSTANCE ferromagnetic substance All the above Solution :A magnet , paramagnetic substance and a ferromagnetic substance are attacted by MAGNETS .

Discussion

Explore topic-wise InterviewSolutions in .

Draw a circle of about 1m diameter on the ground.Ask one of your friends to stand at the centre of this circle.You revolve around your friend in such a manner that your face always remains towards him . Can your friend see your back?

A mirror changes the direction ofligh that falls on it, Can you tell in which direction, the light falling on a surface will be reflected?

Have you ever seen a game of tug-of war? In this game two teams pull at a rope in opposite directions (Fig.11.5). Members of both the teams try to pull the rope in their direction. Sometimes the rope simply does not move. Is it not similar to the situation shown in Fig.11.3(b)?

Fill in the blanks : The outer planets have large number of ___________

Define the following: Angle of reflection

When does a force come into play?

Fill in the blanks : The electric charges generated by rubbing are______.

The iron rims are fitted to the wooden wheels of bullock carts and tongas by process of ____

Do you remember lightning is an electrical discharge?

A cubic lump of cheese of area 10 "cm"^2 and weight 3 N stands on a table. Calculate the pressure exerted by it on the table?

Suggest a method to fill water in a tank constructed at a height of 10 m from the ground by using a vacuum pump instead of an electric pump.

A cuboid of dimensions 3 m xx 2m xx 1m is placed on a surface such that the face with maximum surface area is in contact. If the weight of the cuboid is 1kg_(wt), the pressure exerted by it on the surface is _____. (take g=10 m s^(-2)).

Which of the following has the highest calorific value ?

Can a charged body 'A' having a very small charge on it, be used to charge an uncharged body 'B' , such that the charge acquired by 'B' is many times more than that on 'A'? If so, how? Explain.

Find the volume of 900 g of cooking oil whose density is 0.9 "g/cm"^3. Give the answer in litres.

Explain why we take short steps while walking on slippery surfaces.

How is lightning cause?

Fill in the blanks in the following. If you touch your________ ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with________.

Name the different kinds of charge.

why earth can be considerd as a huge bar magnet.

An electric kettle of power 2 kW is used for 1 minute. Find the energy supplied by the kettle.

Explain why it is not possible to magnetise an iron rod beyond a certain limit ?

The weather department has predicted that a thunderstorm is likely to occur on a certain day. Suppose you have to go out on that day. Would you carry an umbrella? Explain.

If the stars appear to move from east to west, could it mean that the Earth, rotates from west to east?

Fill in the blanks- with suitable words. Unwanted sound is called

What do you mean by luminous objects? Give examples.

The density of a given mass of a gas when 10 Pa pressure acts on it is 2 kg m^(-3). Calculate the density of the gas if the pressure is increased by 5 Pa at constant temperature.

Name the largest planet of the Solar System.

Match the entries given in column A with appropriate ones in column B

Fill in the blanks: The two wires attached to a LED are called ___.

What happens if earthing is not proper in a telegraph ?

An ebonite rod is rubbed with fur or wool. What type of charges do theyacquire ?

What is non-contact force?

Give an example where low inertia is preferred and an example where high inertia is recommended.

Compare the sound of a baby with that of an adult. Is there any difference?

How does the vocal cord affect the quality of voice?

A clock has its minut hand 14 cm long. At what speed and at what velocity does the tip of the minute hand move in a half an hour duration ?

Calculate the area of a body which experiences a pressure of 60 kPa by a force of 12,000 N.

The process of burning a material in theabsence of oxygen is called destructive distillation.

Under what conditions air can conduct electricity?

Define gravitational force.

Fill in the blanks : The sense of________ is one of the most important senses.

State whether the following statements are true orfalse : Friction causes wastage of energy.

In a nuclear reactor, the energy is released by bormbarding uranium nucleaus with _______

A gold leaf electroscope is used for

What is force of friction?

A substance placed near a strong magnet is attracted by it, substance can be _______.

Fill in the blanks in the following. If you touch your ear with right hand in front of a plane mirror it will be seen in the mirror that your right ear is touched with.