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

351.	Look at the sky on a dark,clear night.You see the entire sky dotted with countless stars some bright and some not so bright Observe them carefully. Do you find any star-like object which does not twinkle?
Answer» ANSWER :Yes,there are star-like objects in the sky which do not twinkle. These are called PLANETS.

Discussion

352.	Look at the sky on a dark,clear night.You see the entire sky dotted with countless stars some bright and some not so bright Observe them carefully. Do all of them appear to twinkle?
Answer» ANSWER :No,all the STARS do not APPEAR to TWINKLE.

Discussion

353.	Mark the following statements as true (T) or false (F) . Mercury is the smallest planet of the Solar System
Answer» ANSWER :T

Discussion

354.	In Figure A, draw the reflected ray from the mirror and refracted rayinto the air.
Answer» Solution :`anglei=angler` .REFRACTED ray GOES from denser medium to RARER medium.

Discussion

355.	Mark the following statements as true (T) or false (F) . There are nine planets in the Solar System
Answer» ANSWER :F

Discussion

356.	Fill in the blanks. Sprinkling of powder of the carom board ________ friction.
Answer» ANSWER :REDUCES

Discussion

357.	Which of the following is NOT a planet of the Sun?
Answer» Sirius Mercury Saturn Earth Answer :A

Discussion

358.	Can we hear any sound on the moon?
Answer» Answer :No,we cannot HEAR any SOUND on the moon as there is no atmosphere on the moonand sound needs a medium to TRAVEL.

Discussion

359.	What do you mean by vibration?
Answer» Answer :When an object MOVES to and fro or BACK and forth RAPIDLY, it is CALLED vibration. It is ALSO called oscillatory motion.

Discussion

360.	How do you locate a current-carrying wire concealed in a wall?
Answer» Solution :(i) Current carrying wire-magnetic FIELD. (II) COMPASS needle.

Discussion

361.	A piece of cloth is soaked in kerosene and another piece in water. When both are lighted with a match stick, which one will burn easily ? Why ?
Answer» SOLUTION :(i) Ingition TEMPERATURE of a substance (ii) Cloth SOAKED in kerosene

Discussion

362.	The rate at which ice melts is more at the top when compared to the bottom of the blacier. Explain whether the statement is true capacities.?
Answer» SOLUTION :Where does the WEIGHT of the blacier act? Is the pressure the bottom of the glacier more than at any other part of the glacier? ltbr. How does the presure variation affect the melting point of the ice? When pressure increases, does the M.P. of the ice come down below `0^(@)C`, or does it INCREASE?

Discussion

363.	Define noise.
Answer» ANSWER :Sound which is UNPLEASANT to our ears is CALLED noise. For example, SOUNDS produced by HORNS of vehicles, loudspeakers, television and transistor radio in high volume, etc.

Discussion

364.	Which of the following properties are suitable for making cooking utensils?
Answer» HIGH SPECIFIC heat and high conductivity. Low specific heat and low conductivity High specific heat and low conductivity. Low specific heat and high conductivity. Solution :Low specific heat and high conductivity ar thhe properties which are suitable for MAKING UTENSILS.

Discussion

365.	Gurmit wanted to perform Activity16.8 using laser torch.Her teacher advised her not to do so. Can you explain the basis of the teacher’s advise?
Answer» Answer :GURMIT should not perform Activity16.8 using a laser torch. Her TEACHER advised her not to do so because laser light is harmful for the EYES and MAY cause permanent damage to the retina.

Discussion

366.	Name one non-metal which is a good conductor of electricity.
Answer» ANSWER :GRAPHITE is a non-metal which is a GOOD CONDUCTOR of ELECTRICITY.

Discussion

367.	The 10% of total volume of the barometer liquid (mercury) contains impurities having an average density 5 g cm^(-3). When this faulty barometer is used to measure the atmospheric pressure it reads 80 cm of the liquid column. Determine the correct atmospheric pressure.
Answer» Solution :(i) Volume of impurity =0.1 V Volume of `H_("mercury")=0.9 V` Density of the liquid in BAROMETER `=("total mass")/("total volume")` i.e., `d_(1)=(d_(Hg)xx0.9V + d_("impurity")xx 0.1 V)/(V)` Now the pressure recorded by a standard barometer `P_(1)=h_(Hg) d_(y) g` Pressure recorded by faulty barometer `P_(2)=h_(2)xx dl xx g` Equate (1) and (2) and DETERMINE value at `h_(Hg)`. (II) 75 cm

Discussion

368.	Fuels that have_____catch fire easily.
Answer» ANSWER :LOW IGNITION TEMPERATURE

Discussion

369.	A bird sitting on a tree top at a heigth of 10 m from the ground picks up sticks lying on the ground to build anest on the tree top. It starts picking up the sticsk at 7:00 a.m. and ends up 7:10 a.m. During this interval it makes 5 trips up and down. Find the averae speed and average velocity of the bird
Answer» Solution : Total distacne travelled `=2xx10xx5xx5=10m` Time taken `=7:10-7:00.a.m=10` minutes `=10xx60s=600s` Averge speed = `("Total distance")/("Total time")` `=(100)/(600)=(1)/(6) MS^(-1)` `=0.166 ms^(-1)` Total displacement = ZERO `:.` Average velocity= zero

Discussion

370.	Ice cubes at 0^(@)C each of mass 200 g are dropped one after the other into 2 kg water at 30^(@)C in such a awayy that after the first one melts completely, the second one is dropped. If the heat energy required to melt 1 g of ice is 80 cal, determine the maximum number of ice ice cubes that can be dropped into the water such that no ice is left in the water without melting.
Answer» SOLUTION :HEAT lost by water=head GAINED by ice `ms_(w)(t_(2)-t_(1))=nml` `(2xx103)xx1xx(30-00)=nxx200xx80` `impliesn=3.75` ice cubes.

Discussion

371.	A cone resting on its apex is an example of
Answer» UNSTABLE EQUILIBRIUM STABLE equilibrium neutral equilibrium None of these Answer :A

Discussion

372.	Fill in the blanks : Charged objects made of the same material______ each other.
Answer» ANSWER :REPEL

Discussion

373.	Explain why ' magnetic field lines never intersect with each other'.
Answer» Solution :(i) What happens to the direction of MAGNETIC field at a POINT if two magnetic lines of force intersect each other ? (II) Will there be two direction for the magnetic field at such a GIVEN point ?

Discussion

374.	A pressure exerted by mercury at the bottom of a container of area of cross section 2 cm^(2) is 10 Pa. Determine the weight of the mercury in the container.
Answer» <P> SOLUTION :PRESSURE `P=("Thrust(weight)")/("Area")` Thrust =Area `xx` pressure `=2xx10-4xx10=2xx10^(-3)N` Weight of mercury `=2xx10^(-3) N`.

Discussion

375.	The density of sand is 1500 "kg/m"^3. What is the mass of 1m^3 of sand ?
Answer» ANSWER :1500 KG

Discussion

376.	What other objects do you see in the night sky?
Answer» Answer :In the NIGHT sky, besides MOON, we SEE a LARGE numberof STARS twinkling.

Discussion

377.	An object suspended from a sensitive spring balance is placed inside a closed container. The other end of the container is closed by means of an air tight piston. Will there by any change in the spring balance reading when the piston is moved the inward and outward direction ? Why ?
Answer» SOLUTION :APPARENT WEIGHT = ACTUAL weight - UPTHRUST

Discussion

378.	Have you ever wondered what makes an object slow down or go faster, or change its direction of motion?
Answer» Answer :Application of FORCE on an object makes it SLOW down or go faster, or change its DIRECTION of motion.

Discussion

379.	Which among the following has carbon as the positive electrode?
Answer» Lechanche BICHROMATE CELL DRY cell All of the above Answer :D

Discussion

380.	Fill in the blanks. Friction depends on the _________ of surfaces.
Answer» ANSWER :NATURE

Discussion

381.	The oscillation of a simple pendulum is graphically represented as follows. Determine the (a) time period (b) frequency (c) amplitude
Answer» Solution :(a) Time PERIOD = 6s (b) FREQUENCY `(1)/(T) = (1)/(6) Hz` (c) AMPLITUDE = 5 cm

Discussion

382.	What is sliding friction?
Answer» Answer :The FORCE needed to KEEP a moving OBJECT in motion at a constant speed is called SLIDING friction.

Discussion

383.	Fill in the blanks: Vegetable oil, kerosene oil and honey cannot conduct ___.
Answer» ANSWER :ELECTRICITY

Discussion

384.	The moment of a force of 50 N about a point is 5 Nm. Find the perpendicular distance of force from that point.
Answer» ANSWER :0.1 m

Discussion

385.	What does frequency determine in sound?
Answer» Answer :The shrillness or PITCH of a sound is DETERMINED by its FREQUENCY.

Discussion

386.	Magnetic lines of force are
Answer» DIRECTED from the north pole to south pole in the MAGNETIC field. directed from the south pole to north pole INSIDE a magnet. closed loops All the above Answer :D

Discussion

387.	What is a ray of light?
Answer» Answer :A RAY of light is the straightline path of PROPAGATION of light.It is in reality an arrowbeam of light constituting SEVERAL light RAYS.

Discussion

388.	Using a compass needle low would you distinguish between three bars similar in shape and appearance if one is brass, the second is an unmagnetised iron and the third is a permanent magnet ?
Answer» Solution :(i) DEFINITION of magnetic MERIDIAN (ii) USUALLY to determine the magnetic meridian we use a magnetic compass and the magnetic needle inside it is FIXED in a horizontal plane.

Discussion

389.	It is advised not to stand near a running train. Why?
Answer» Solution :What is BERNOULLIS' principle ? What happens to the PRESSURE near the MOVING train ? When pressure difference is CREATED, then do things move from HIGHER pressure area to a low pressure area ?

Discussion

390.	Choose the correct match. {:("(i) Primary succession","(a) Fast"),("(ii) Secondary succession","(b) Cooled volcanic lava"),(,"(c) Slow"),(,"(d) Abandoned farm land"):}
Answer» A-b,B-C,C-a A-c,B-a,C-b A-b,B-a,C-c A-a,B-c,C-b Answer :C

Discussion

391.	Define the following: Normal
Answer» Answer :Normal:A normal is the perpendicular LINE(90°) DRAWN at the point of incidence on the incident SURFACE.

Discussion

392.	In an unmagnetised iron bar, the molecules form _______.
Answer» CIRCULAR chains long STRAIGHT chains closed chains opposite, parallel chains Solution :According to Ewing's molecular theory, in unmagnetised iron bar, the molecular MAGNETS FORM closed chains.

Discussion

393.	A car is lifted by a hydraulic jack that consists of two pistons. The diameter of the larger piston is 2 m and that of the smaller piston is 50 cm. If the force applied on the smaller piston is 240 N, find the weight of the car.
Answer» Solution :(i) Give principle of Bramah's PRESS. What is Pascal's LAW ? Give the area of cross-section of the two pistons. Substitute the values in the formula, `(F_(1))/(A_(1))=(F_(2))/(A_(2))` FIND the VALUE of `'F_(2)'` (ii) 3840 N

Discussion

394.	How is friction caused?
Answer» ANSWER :When the IRREGULARITIES in the surfaces of two OBJECTS come into contact with each other, it causes friction.

Discussion

395.	The line drawn in the direction of force is called the line of action of that force.
Answer» Solution :The line drawn in the direction of FORCE is CALLED line of ACTION of that force i.e. is a geometric REPRESENTATION of how the force is applied.

Discussion

396.	A load weighing 20,000 N is placed on a side with area 1000 "cm"^2. How much pressure would it exert on the ground?
Answer» Solution :Force APPLIED by the load (F)=20,000 N Area (A)= `1000 "cm"^2` `=1000// (100xx100 m^2)=0.1 m^2` PRESSURE (P)=F/A=`20,000 N//0.1 m^2` `=2xx10^5` Pa

Discussion

397.	Just think: would it be possible to hold the glass at all if there is no friction?
Answer» Answer :No, it WOULD not be POSSIBLE to hold the GLASS without any friction.

Discussion

398.	Which of the following is a mechanical wave?
Answer» sound Light Radio All the above Answer :A

Discussion

399.	The instruments that produce sound by vibrating strings are called _____
Answer» ANSWER :STRING INSTRUMENTS

Discussion

400.	Suppose you have a balloon which has holes. Would you be able to inflate it? If not, why? Can we say that air excerts pressure in all directions?
Answer» ANSWER :No, a balloon with HOLES in it cannot be inflated. It cannot be inflated because AIR will ESCAPE from the holes and will not be ABLE to excert.

Discussion

Explore topic-wise InterviewSolutions in .

Look at the sky on a dark,clear night.You see the entire sky dotted with countless stars some bright and some not so bright Observe them carefully. Do you find any star-like object which does not twinkle?

Look at the sky on a dark,clear night.You see the entire sky dotted with countless stars some bright and some not so bright Observe them carefully. Do all of them appear to twinkle?

Mark the following statements as true (T) or false (F) . Mercury is the smallest planet of the Solar System

In Figure A, draw the reflected ray from the mirror and refracted rayinto the air.

Mark the following statements as true (T) or false (F) . There are nine planets in the Solar System

Fill in the blanks. Sprinkling of powder of the carom board ________ friction.

Which of the following is NOT a planet of the Sun?

Can we hear any sound on the moon?

What do you mean by vibration?

How do you locate a current-carrying wire concealed in a wall?

A piece of cloth is soaked in kerosene and another piece in water. When both are lighted with a match stick, which one will burn easily ? Why ?

The rate at which ice melts is more at the top when compared to the bottom of the blacier. Explain whether the statement is true capacities.?

Define noise.

Which of the following properties are suitable for making cooking utensils?

Gurmit wanted to perform Activity16.8 using laser torch.Her teacher advised her not to do so. Can you explain the basis of the teacher’s advise?

Name one non-metal which is a good conductor of electricity.

The 10% of total volume of the barometer liquid (mercury) contains impurities having an average density 5 g cm^(-3). When this faulty barometer is used to measure the atmospheric pressure it reads 80 cm of the liquid column. Determine the correct atmospheric pressure.

Fuels that have_____catch fire easily.

A cone resting on its apex is an example of

Fill in the blanks : Charged objects made of the same material______ each other.

Explain why ' magnetic field lines never intersect with each other'.

A pressure exerted by mercury at the bottom of a container of area of cross section 2 cm^(2) is 10 Pa. Determine the weight of the mercury in the container.

The density of sand is 1500 "kg/m"^3. What is the mass of 1m^3 of sand ?

What other objects do you see in the night sky?

An object suspended from a sensitive spring balance is placed inside a closed container. The other end of the container is closed by means of an air tight piston. Will there by any change in the spring balance reading when the piston is moved the inward and outward direction ? Why ?

Have you ever wondered what makes an object slow down or go faster, or change its direction of motion?

Which among the following has carbon as the positive electrode?

Fill in the blanks. Friction depends on the _________ of surfaces.

The oscillation of a simple pendulum is graphically represented as follows. Determine the (a) time period (b) frequency (c) amplitude

What is sliding friction?

Fill in the blanks: Vegetable oil, kerosene oil and honey cannot conduct ___.

The moment of a force of 50 N about a point is 5 Nm. Find the perpendicular distance of force from that point.

What does frequency determine in sound?

Magnetic lines of force are

What is a ray of light?

Using a compass needle low would you distinguish between three bars similar in shape and appearance if one is brass, the second is an unmagnetised iron and the third is a permanent magnet ?

It is advised not to stand near a running train. Why?

Choose the correct match. {:("(i) Primary succession","(a) Fast"),("(ii) Secondary succession","(b) Cooled volcanic lava"),(,"(c) Slow"),(,"(d) Abandoned farm land"):}

Define the following: Normal

In an unmagnetised iron bar, the molecules form _______.

A car is lifted by a hydraulic jack that consists of two pistons. The diameter of the larger piston is 2 m and that of the smaller piston is 50 cm. If the force applied on the smaller piston is 240 N, find the weight of the car.

How is friction caused?

The line drawn in the direction of force is called the line of action of that force.

A load weighing 20,000 N is placed on a side with area 1000 "cm"^2. How much pressure would it exert on the ground?

Just think: would it be possible to hold the glass at all if there is no friction?

Which of the following is a mechanical wave?

The instruments that produce sound by vibrating strings are called _____

Suppose you have a balloon which has holes. Would you be able to inflate it? If not, why? Can we say that air excerts pressure in all directions?