885 + Interview Questions in Physics in Class 8 Page 4 InterviewSolution

151.	State whether the following statement is true or false: State of zero speed is said to be a state of rest.
Answer» ANSWER :1

Discussion

152.	What happends when you apply a force on an inflated balloon by pressing it between your palms?
Answer» Answer :We notice a change in the SHAPE of an inflated BALLOON when we apply force on it by PRESSING it between our palms.

Discussion

153.	A bottle standing on its base is more stable than when it stands on its neck. This is so because when it stands on the base its ______.
Answer» BASE AREA is more centre of gravity is nearer to the base centre of gravity is at the top Both (a) and (b). Solution :A BOTTLE standing on the base is more stable because its base area is more and the position of the centre of gravity is as low.

Discussion

154.	Does it mean that the net force on an object is zero if the two forces acting on it in opposite directions are equal?
Answer» ANSWER :Yes, if the TWO forces acting on it in opposite directions are equal then the net force on an OBJECT is zero.

Discussion

155.	When a glass rod is rubbed with a piece of silk cloth the rod
Answer» and the CLOTH both acquire POSITIVE charge. becomes positively charged while the cloth has a negative charge. and the cloth both acquire negative charge. becomes negatively charged while the cloth has a positive charge. Answer :A::B::C::D

Discussion

156.	When a stationary vehicle suddenly starts, the persons in it tend to fall backward. This is due to
Answer» INERTIA of REST inertia of MOTION inertia of direction All the above Answer :A

Discussion

157.	A car acceletrates uniformaly at 4 m s^(-2) froms rest. Find its velocity at the end of 5 seconds.
Answer» Solution :Given ACCELERATION of the car, `a=4 m s^(-2)` Initial velocitt of the car,` u=0 m s^(-1)` TIME INTERVAL, t=5s Final velocity of the car,` v=u+at` `=0+(4)(5)` `=20 m s^(-1)`

Discussion

158.	Under normal conditions, naphthalene changes its state from______
Answer» SOLID to liquid liquid to gas liquid to solid solid to gas Answer :D

Discussion

159.	Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?
Answer» ANSWER :the DESTRUCTIVE ENERGY of an earthquake is MEASURED on a Richter CALE.

Discussion

160.	Friction in moving parts of a machine can be reduced by using ______.
Answer» lubricants BALL bearings iron filings Both (a) and (B). Solution :FRICTION in moving parts a machine can be reduced by USING lubricants and ball bearings.

Discussion

161.	Fill in the blanks : Force excerted perunit area is called ________.
Answer» ANSWER :PRESSURE.

Discussion

162.	If a girl is wearing a pointed heel which has an area of cross section 2 "cm"^2, and if her mass is 650 N, find out the pressure exerted by her on the floor (remember to calculate for both legs)
Answer» ANSWER :1625 KPA

Discussion

163.	Why do the Sun appears to rise in the east and set in the west?
Answer» Answer :The SUN appears to rise in the east and SET in the WEST because the EARTH ROTATES on its axis from west to east.

Discussion

164.	Choose the correct answer. Voice of which of the following is likely to have minimum frequency?
Answer» BABY girl Baby boy A man A woman. Answer :C

Discussion

165.	Fill in the blanks in the following statement. To move a loaded trolley we have to _______ it.
Answer» ANSWER :EITHER PULL or PUSH

Discussion

166.	A surface of area 1 m^(2) kept perpendicular to the sun rays absorbs 3 MJ solar energy in one hour. (a) What is the amount of solar energy absorbed by a solar heater when a surface of area of 9 cm^(2) is exposed perpendicular to the sun rays for 4 hours. (b) What is amount of time taken by this heater to boil 12 kg of water at 40^(@)C if its efficiency is 60% ? specific heat capacity of water =4200 J kg^(-1) .^(@)C^(-1)
Answer» SOLUTION :(i) `Q =msDeltat`(II) 567 KJ

Discussion

167.	An electric bell works on the principle of ______
Answer» magnetic induction ATTRACTIVE PROPERTY of magnets electromagntism All the above Solution :The WORKING of an electric bell involves magnetic induction, attractive property of magnets and electromagnetism

Discussion

168.	Volcanic eruption polluents air, by releasing_____and _______into the air.
Answer» ANSWER :`SO_(2),`ASH

Discussion

169.	The source of energy, which cannot be replenished after usage are termed as ________.
Answer» ANSWER :Non-renewable SOURCE of ENERGY

Discussion

170.	Fill in the blanks. Friction produces _________
Answer» ANSWER :HEAT

Discussion

171.	What is the use of glass bulb in an electric bulb? Can we use an electric bulb without the glass bulb in space?
Answer» SOLUTION : FILAMENT should not be in CONTACT with OXYGEN

Discussion

172.	A force of 1000 N acts on an area of 0.050 m^2. Find the pressure in pascals.
Answer» ANSWER :20 KPA

Discussion

173.	A sound wave travels 60m in the time taken to produce 50 waves. Find the wavelength of the sound wave in centimeters
Answer» SOLUTION :(i) ONE WAVE is equal to one wavelength (II) 120 cm

Discussion

174.	A man can lift a maximum weight of 30 kg_("wt"). In order to lift an object of weight 50 kg placed in a container, he pours a certain liquid into the container so that the object is completely immersed in it. What is the density of the liquid if he can just lift the object ? The volume of the liquid displaced is 10^(-2) m^(3).
Answer» Solution :(i) APPARENT weight =Actual Weight -UPTHRUST Upthrust `=V_(1)xxd_(1)xxg` (II) `2 g cm^(-3), ("or") 2000 kg m^(-3)`.

Discussion

175.	Fill in the blanks : Eyelids________ light when not required.
Answer» ANSWER :SHUT out

Discussion

176.	A boy kicks a football horizontally from the roof of a building of height 10m, . If the line joining the initial position of the football and the point where it hits the ground make anangle of 45^(@) with the ground, then find the displacement of the football
Answer» SOLUTION :The SITUATION is as show in the following diagram. The height of the building is respresented by AO.The football is HIT from point A and it hits thr ground at B. Triangle OABj is an isoseceles rigth-angled triangle. Therefore, , AO=OB=10m `AB=sqrt(OA^(2)+OB^(2))=sqrt(10^(2)+10^(2))=sqrt(200)` `AB=10sqrt(2)m` Displacement `=10sqrt(2)m`

Discussion

177.	Repulsion is a sure test for magnetism.
Answer» ANSWER :T

Discussion

178.	Which of the follwing molecular species does not exist?
Answer» saturaiton point of magnetisation. existence of TWO POLES in a magnet. paramagnetism none of the above Solution :Ewing's molecular theory was ABLE to explain saturation point of magnetism and existence of two poles in a magnet. But it was not able to explain the difference between paramagnetic, diamagnetic and ferromagnetic substance.

Discussion

179.	Which of the following statements is/are true regarding hydel energy ? (A) Moving water is a source of energy. (B) it is renewable source. (C) contruct of reservoir is not expensive.
Answer» A and B A and C A,B,C None of the above ANSWER :A

Discussion

180.	Does it give you an idea how large the atmosperic pressure is?
Answer» ANSWER :YES, it proves that ATMOSPHERIC pressure is too LARGE.

Discussion

181.	Two metallic spheres 'P' and 'Q' weighing 200 gwt and 150 gwt, respectively, balance each other when immersed in water. If the relative density of 'P' is 2 find the specific gravity of 'Q'.
Answer» Solution :Weight of P in air, `W_(1p)=200 gwt` Let weight of P in water be `W_(2p)` `therefore` the apparent loss of weight of 'P' in water `=W_(1p)-W_(2p)` `therefore` the relative DENSITY of 'P' `(W_(1p))/(W_(1p)-W_(2p))=2` (given) `therefore (200)/(200-W_(2p))=2 implies W_(2p)` `=200(1-(1)/(2))=100g _(WT)` Weight of 'Q' in ARI, `W_(1q)=150` gwt Let weight of 'Q' in water be `W_(2p)` `therefore` the apparent loss of weight of 'Q' in water `=W_(1p)-W_(2p)=150-W_(2q)` But `W_(2p)=W_(2q)` `therefore` apparent loss of weight of 'Q' in water =150-100=50 gwt `therefore` the specific gravity of `Q=(W_(1q))/(W_(1q)-W_(2q))=(150)/(50)=3`

Discussion

182.	What is the purpose of an electroscope?
Answer» Answer :An electroscope is used to TEST WHETHER an OBJECT is charged or not.

Discussion

183.	An object floats in water such that half of its volume is immersed in it. The specific gravity of the object is _____.
Answer» SOLUTION :N//A

Discussion

184.	Volume of water is aburette is 35 ml. Find the volume of a drop of water if volume of water in the burette is 5 ml when 50 drops of water drained out
Answer» Solution :Voume of single DROP of WATER `= (35-5)/(50)=0.6 "ML"`

Discussion

185.	What is drag?
Answer» ANSWER :DRAG is the FRICTIONAL force exerted by FLUIDS.

Discussion

186.	Fill in the blanks- with suitable words. Loudness is determined by the _________ of vibration.
Answer» ANSWER :A::D

Discussion

187.	Fill in the blanks : To move an object from rest is _________ than moving an object already in motion.
Answer» ANSWER :DIFFICULT

Discussion

188.	The centre of gravity of a ring is situated ______.
Answer» INSIDE the material of the ring OUTSIDE the material of the ring at the CENTRE outside the material of the ring anywhere away from the centre None of the above Solution :The centre of GRAVITY of a ring is situated outside the material of the body, at the centre

Discussion

189.	The fuels that cannot be replenished, once they are used, are called_________
Answer» RENEWABLE sources non-renewable sources ultimate sources accessible sources Answer :B

Discussion

190.	If a bar of steel is placed in a solenoid, then it changes to________ .
Answer» an ELECTRIC bell an electromagnet a dynamo a PERMANENT magnet Answer :D

Discussion

191.	Some renewable sources of energy are given below : solar energy, tidal energy, biogas energy, hydel energy , OTEC, wind energy, geothermal energy, ocean wave energy. Which of the given sources are more reliable and consistent in availability.
Answer» Solution :From AMONG the given SOURCES of energy find those which are available throughout the year irrespective of CLIMATIC changes. Are the REMAINING sources of energy of no ADVANTAGE ?

Discussion

192.	The temperature of a body is measured in Kelvin scale, Fahrenheit scale and Celsius scale. Which among them is a more accurate reading? Explain.
Answer» SOLUTION :NUMBE rof DIVISON between LFP and UFP in FAHRENHEIT scale is 180 which is more THN that on kelvin or celcius scale.

Discussion

193.	if specific heat capacity of mercury is 0.033 cal g^(-1)" ".^(@)C^(-1), how much heat is gained by 0.05 kg of mercury when its temperature rises from 68^(@)F to 313K?
Answer» Solution :The INITIAL temperature `=68^(@)F` `[(5)/(9)(68-32)].^(@)C=20C^(@)` FINAL temperature `=313K=(313-273).^(@)C=40^(@)C` Mass of mercury given `=0.05kg=50g` Specific heat CAPACITY of mercury =0.033 cal `g^(-1).^(@)C^(-1) I.e., heat gained by 1 g of mercury for `1^(@)C` rise =0.033 cal hence, gained by 1 g of mercury for `1^(@)C` rise =0.033`xx50=1.65cal` `therefore` hear gained by 50 g mercury for `20^(@)C` rise =33 cal

Discussion

194.	A boy has a mass of 55 kg. He climbs 10 m up a tree. What is his gravitational potential energy?
Answer» SOLUTION :m=55 kg , h=10 m, `g=10 m//s^2` PE=m X g x h = 55 x 10 x 10 = 5500 J or 5.5 KJ

Discussion

195.	The heat capacity of a vessel is 300 cal .^(@)C^(-1) and the heat capacity of water contained in the vessel is also 300 cal .^(@)C^(-1). How much heat (in joules) is required to raise the temperature of water in the vessel by 126^(@)F?
Answer» Solution :A rise in temeprature of `9^(@)C` is equal to a rise in temperature of `5.^(@)C`. `therefore`A rise in temperature of 126 `.^(@)F` is on the celsius SCALE EQUIVALENT to `126xx(5)/(9)=14xx5=70.^(@)C` quantity of heat required to RAISE the temperature of the vessel by `1.^(@)C=300cal` ltBrgt `therefore` Heat requried to raise its temperature by ltBrgt `70.^(@)C=70xx300=21000` cal. SIMILARLY heat required to raise the temperature of water by `70.^(@)C=70xx300=21000cal` `therefore` the TOTAL heat required `=(21000+21000)cal=42000cal` `=4200xx4.2=176.4kJ`

Discussion

196.	Observe this constellation for a few hours. Do you find any change in its shape? You will observe that the shape of the constellation remains the same. You will find that the constellationappears to move in the sky from east to west.
Answer» Answer :No, the shape of the CONSTELLATION DOESNOT CHANGE,in FACT it REMAINS the same.

Discussion

197.	To obtain of water at 50^(@)C, how many grams of stea at its stea point must be passed to 70 g of ice at 0^(@)C.
Answer» SOLUTION : HEAT PRODUCED by steam=Heat ABSORBED by ICE. `M[590]=5600+3500` `M=(9100)/(590)=910//59g=15.42g`

Discussion

198.	The above diagrame is the pattern of magnetic lines of force obtained when two magnets are placed with their magnetic axes coinciding. The magnetic poles x and y are______and ________respectively.
Answer» NORTH , SOUTH south , north north , north south , south Answer :D

Discussion

199.	Fill in the blanks : If two forces acting on an object in opposite directions are equal then the net force acting on it will be ______.
Answer» ANSWER :ZERO

Discussion

200.	Fill in the following blanks which suitable words : (a) The lines of ......round a straight current-carryingconductor are in the shape of......... (b) For a current-carrying solenoid, the magnetic field is like that of a .......... (c) The magnetic effect of a coilcan be increased by increasing the number of ........,increasing the ................., or inserting an ................. core. (d) If a coil is viewed from one end and the current flows inan anticlockwise direction, then this end is a .......... pole. (e) If a coil is viewed from one end, and the current flows in a clockwise direction,then this end is a ...... pole.
Answer» ANSWER :SOUTH

Discussion

Explore topic-wise InterviewSolutions in .

State whether the following statement is true or false: State of zero speed is said to be a state of rest.

What happends when you apply a force on an inflated balloon by pressing it between your palms?

A bottle standing on its base is more stable than when it stands on its neck. This is so because when it stands on the base its ______.

Does it mean that the net force on an object is zero if the two forces acting on it in opposite directions are equal?

When a glass rod is rubbed with a piece of silk cloth the rod

When a stationary vehicle suddenly starts, the persons in it tend to fall backward. This is due to

A car acceletrates uniformaly at 4 m s^(-2) froms rest. Find its velocity at the end of 5 seconds.

Under normal conditions, naphthalene changes its state from______

Name the scale on which the destructive energy of an earthquake is measured. An earthquake measures 3 on this scale. Would it be recorded by a seismograph? Is it likely to cause much damage?

Friction in moving parts of a machine can be reduced by using ______.

Fill in the blanks : Force excerted perunit area is called ________.

If a girl is wearing a pointed heel which has an area of cross section 2 "cm"^2, and if her mass is 650 N, find out the pressure exerted by her on the floor (remember to calculate for both legs)

Why do the Sun appears to rise in the east and set in the west?

Choose the correct answer. Voice of which of the following is likely to have minimum frequency?

Fill in the blanks in the following statement. To move a loaded trolley we have to _______ it.

An electric bell works on the principle of ______

Volcanic eruption polluents air, by releasing_____and _______into the air.

The source of energy, which cannot be replenished after usage are termed as ________.

Fill in the blanks. Friction produces _________

What is the use of glass bulb in an electric bulb? Can we use an electric bulb without the glass bulb in space?

A force of 1000 N acts on an area of 0.050 m^2. Find the pressure in pascals.

A sound wave travels 60m in the time taken to produce 50 waves. Find the wavelength of the sound wave in centimeters

Fill in the blanks : Eyelids________ light when not required.

A boy kicks a football horizontally from the roof of a building of height 10m, . If the line joining the initial position of the football and the point where it hits the ground make anangle of 45^(@) with the ground, then find the displacement of the football

Repulsion is a sure test for magnetism.

Which of the follwing molecular species does not exist?

Which of the following statements is/are true regarding hydel energy ? (A) Moving water is a source of energy. (B) it is renewable source. (C) contruct of reservoir is not expensive.

Does it give you an idea how large the atmosperic pressure is?

Two metallic spheres 'P' and 'Q' weighing 200 gwt and 150 gwt, respectively, balance each other when immersed in water. If the relative density of 'P' is 2 find the specific gravity of 'Q'.

What is the purpose of an electroscope?

An object floats in water such that half of its volume is immersed in it. The specific gravity of the object is _____.

Volume of water is aburette is 35 ml. Find the volume of a drop of water if volume of water in the burette is 5 ml when 50 drops of water drained out

What is drag?

Fill in the blanks- with suitable words. Loudness is determined by the _________ of vibration.

Fill in the blanks : To move an object from rest is _________ than moving an object already in motion.

The centre of gravity of a ring is situated ______.

The fuels that cannot be replenished, once they are used, are called_________

If a bar of steel is placed in a solenoid, then it changes to________ .

Some renewable sources of energy are given below : solar energy, tidal energy, biogas energy, hydel energy , OTEC, wind energy, geothermal energy, ocean wave energy. Which of the given sources are more reliable and consistent in availability.

The temperature of a body is measured in Kelvin scale, Fahrenheit scale and Celsius scale. Which among them is a more accurate reading? Explain.

if specific heat capacity of mercury is 0.033 cal g^(-1)" ".^(@)C^(-1), how much heat is gained by 0.05 kg of mercury when its temperature rises from 68^(@)F to 313K?

A boy has a mass of 55 kg. He climbs 10 m up a tree. What is his gravitational potential energy?

The heat capacity of a vessel is 300 cal .^(@)C^(-1) and the heat capacity of water contained in the vessel is also 300 cal .^(@)C^(-1). How much heat (in joules) is required to raise the temperature of water in the vessel by 126^(@)F?

Observe this constellation for a few hours. Do you find any change in its shape? You will observe that the shape of the constellation remains the same. You will find that the constellationappears to move in the sky from east to west.

To obtain of water at 50^(@)C, how many grams of stea at its stea point must be passed to 70 g of ice at 0^(@)C.

The above diagrame is the pattern of magnetic lines of force obtained when two magnets are placed with their magnetic axes coinciding. The magnetic poles x and y are______and ________respectively.

Fill in the blanks : If two forces acting on an object in opposite directions are equal then the net force acting on it will be ______.

Volcanic eruption polluents air, by releasing_and ___into the air.

The above diagrame is the pattern of magnetic lines of force obtained when two magnets are placed with their magnetic axes coinciding. The magnetic poles x and y areand __respectively.