885 + Interview Questions in Physics in Class 8 Page 13 InterviewSolution

601.	State whether the following statements are true or false : Comets revolve around the Sun in highly elliptical orbits.
Answer» ANSWER :1

Discussion

602.	Time period of simple pendulum increase with
Answer» increases decreases remains same first increases and then decreases Solution :Time PERIOD of a SIMPLE pendulum is inversely proportional to the ACCELERATION due to GRAVITY `T alpha (1)/(sqrtg)`

Discussion

603.	A ginven substance of mass 'm' is in solid state at certain temperature. Arrange the following steps in proper sequence to calcualte the total heat energy required to just convert the substance completely into gaseous state. (a). Note down the specific latent heat of vaporization of the substance and calculate the heat supplied to convert from liquid to gaseous state using the formula. (b) Note down the melting point of the substance and calculate the heat supplied to increase the temperature of the solid to its melting point. (c) Note down the boiling point of the substance and calculate the heat supplied to increase the temperature of the substance from melting point to its boiling point. (d). Add all the heat energies, it gives the resultant hea supplied to the solid to just convert it into gaseous state. (e) Note down the specific latent heat of fusion of the substance and calculate the heat supplied to convert the substance from solid state to liquid state.
Answer» b d e c a a c e d b a b c d e b e c a d Solution :To calculate theh total HEAT energy supplied, first note down the melting point fo te substance and calculate the heat energy supplied to SOLID to increase the temperature to its melting poitn (b). Now calculate the heat energy supplied to the solid to the solid state to convert it into liquid state by taking specific latent heat of fusion (e). Note down the boiling point of the substance and calculate the heat energy supplied to increase the temperature from melting point to boiling point. (c) . Now calculate the heat energy supplied to the liquid at its boiling point to convert it into gaseous state by taking the specific latent heat of vaporization (a). By adding all the heat ENERGIES, we will get the RESULTANT heat supplied to convert solid into gas (d).

Discussion

604.	What is incident ray?
Answer» Answer :An incident RAY is a ray of light striking a reflecting surface such as a MIRROR.

Discussion

605.	State whether the following statements are true or false : A normal eye can clearly see distant objects as well as objects nearby.
Answer» ANSWER :1

Discussion

606.	Assertion (A) : When wind blows at a very high speed over the roof of a hut, the roof is blown away. Reason (R ) : The pressure exerted by a fluid at rest is transmitted unchanged equally in all directions.
Answer» A and R are correct and R is the correct explanation for A. A and R are correct but R is not the correct explanation for A. A is correct but R is wrong. Both A and R are wrong. Solution :When wind BLOWS with high speed over the ROOF of a HUT, the roof is blown away due to the pressure difference created between top and bottom surfaces of the roof . Hence, R is not the correct explanation of A.

Discussion

607.	In the expression buoyant force or upthrust =V xx rho xx g rho is the density of the liquid displaced.
Answer» SOLUTION :N//A

Discussion

608.	If scientists know so much about earthquakes, can they also predict when and where the next one will strike?
Answer» Answer :No, it is not POSSIBLE to PREDICT when and where the NEXT EARTHQUAKE will STRIKE.

Discussion

609.	What are plates?
Answer» Answer :In the uppermost LAYER of the earth, the earth's CRUST is divided into SEVERAL PIECES, each of which is called a PLATE.

Discussion

610.	A new scale fo temperature is introduced. One degree temperature difference on the new scale is found to be equal to (5)/(8).^(@)C. Determine the temperature in Celsium scale when the new scale and the celsium scale shows the saer eading. The lower fixed point on the new scale is 33^(@) degree.
Answer» Solution :On NEW scale, ONE DEGREE temperature DIFFERENCE=`5//8^(@)C` Lower fixed point (LFP) on new scale=33degrees find LEAST count and then, ltBrgt Find temperatrue in new sclae=temperature on Celsium scale.

Discussion

611.	Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon.
Answer» Answer :A charged BALLOON REPELS another charged balloon because CHARGE acquired by same OBJECTS are the same.

Discussion

612.	Who proved that lightning and spark from clothes are the same phenomena and when?
Answer» Answer :BENJAMIN FRANKLIN, an American SCIENTIST, in 1752 proved that lightning and spark from CLOTHES are the same phenomena.

Discussion

613.	The loudness of sound of the bell in the bell jar experiment gradually decreases with _____
Answer» DECREASE in the QUANTITY of air increase in the quantity of air increase in the ATMOSPHERIC pressure None of the above Answer :A

Discussion

614.	Fill inthe blanks. Asteroids are found between the orbits of _____ and _______
Answer» ANSWER :MARS; JUPITER

Discussion

615.	What do you mean by vacuum?
Answer» ANSWER :COMPLETE absence of AIR in a vessel or in a surrounding is called vacuum.

Discussion

616.	Each loop of a solenoid acts like a tiny magnet with north and south poles.
Answer» ANSWER :1

Discussion

617.	The effective length of the magnet shown above is ______.
Answer» y 2y x x/2 Answer :B

Discussion

618.	Now recall what happended when you and your friend pushed the heavy box in the same direction.
Answer» Answer :When I and my FRIEND together pushed the HEAVY BOX in the same diirection, it could be MOVED easily.

Discussion

619.	What dio you mean by force?
Answer» ANSWER :Any KIND of push or pull excerted on an OBJECT is called FORCE.

Discussion

620.	A stone is dropped from the top of a tower and it hits the ground at t = 3.5s. If the velocity of sound in air is 300 ms^(-1), find the time taken to hear the sound by a person on the top of the tower, from the instant the body is dropped (g = 10 ms^(-2))
Answer» SOLUTION :(i) `S = (1)/(2) "GT"^(2), V = (d)/(t)` (ii) `3.75 s`

Discussion

621.	Explain Action and reaction
Answer» always ACT on TWO different BODIES are EQUAL in magnitude are opposite in direction All the above Solution :(i) Action and reaction always act on two different bodies. (2) They are equal in magnitude but opposite in direction.

Discussion

622.	Fill in the blanks in the following. Night birds have________ cones than rods in their eyes.
Answer» ANSWER :LESS

Discussion

623.	If water be used to construct a barometer, what would be the height of water column at a standard atmospheric presure (76cm of mercury)?
Answer» SOLUTION :N//A

Discussion

624.	A hydrometer stem has a length 30 cm. If the hydrometer is immersed in water , its floatation bulb just sinks. If the same hydrometer is immersed in a liquid having density of 500 kg m^(-3), two-third of the stem is immersed. Find the least specific gravity of a liquid that can be measured using the hydrometer.
Answer» Solution :Let 'V' be volume of the hydrometer upto the beginning of its setm (i.e., volume of gravity bulb+floatation bulb) Let 'a' be the area of cross SECTION of the stem. When the hydrometer is immersed in water, `V xx 1`= mass of hydrometer. DENSITY of the given liquid`=500 kg m^(-3)=0.5 g cm^(-3)` Length of the stem immersed in the liquid `=(2)/(3) ("total length")=(2)/(3)xx30=20cm` `therefore` volume of the hydrometer in the liquid =V+20a `therefore ` mass of liquid DISPLACED =(V+20a)0.5=mass of hydrometer `therefore(V+20a)0.5=V IMPLIES V+20a=2V` or `a(V)/(20)` let `RHO` be the density of the liquid on which the hydrometer floats upto its full length of stem. Then mass of hydrometer `=(V+30a)rho=V` `implies rho= (V)/(V+30a)=(V)/(V+30((V)/(20)))` `rho =0.4` `therefore ` least specific gravity of the liquid that can be measured using the hydfrometer is 0.4.

Discussion

625.	For the range of frequencies of sound 11 kHz to 11 find the time taken by a vibrating particle to move from its mean position to the immediate rarefaction.
Answer» Solution :(i) `V = N lamda` (ii) 30 MM to `30 mu m`

Discussion

626.	What do you mean by noise pollution?
Answer» Answer :NOISE pollution means excessive or UNWANTED SOUND PRESENT in the environment that causes DISCOMFORT to our ears.

Discussion

627.	The magnetic compass is not useful for navigation near the magnetic poles because
Answer» ANSWER :T

Discussion

628.	Suggest three measures to protect ourselves from lightning.
Answer» Answer :We should FIND a closed or INDOOR space.While travelling in a car or bus, we should CLOSE the windows and doors COMPLETELY.

Discussion

629.	Which one of the following physical quantities increases as we go deep into the sea ?
Answer» TEMPERATURE gravity pressure upthrust Solution :N//A

Discussion

630.	What can be added to water to make,it more conducting?
Answer» Answer :A TEASPOON of salt or lemon JUICE can be added to MAKE WATER more conducting.

Discussion

631.	It is possible to melt a piece of aluminium placed in a spoon made of zinc.
Answer» Solution :The susceptibility of different BASE metals to corrosion while in contact, depends upon the difference between the contact potentials, or the electromotive voltage of the metals involved. The greater the potential difference is, the greater is the tendency for corrosion. the larger the separation distance in the electromotive chart between the two metals in contact, the HIGHER the contact potential and chances for corrosion. for EXAMPLE, zinc and aluminium are very SHORT distance apart in the cahrt, THEREFORE potential for corrosion when these two metals are in contact is very low. Therefore it is not possible to melt a piece of aluminium placed in a spoon made of zinc.

Discussion

632.	After doing the electroplating activity. Paheli interchanged the eIectrodes and repeated the activity. What do you think that she would observe this time?
Answer» ANSWER :She WOULD Observe that the process ofelectroplating has not taken place this TIME.

Discussion

633.	heat transfer rate is more ini_____
Answer» glass wood plastic copper Solution :Heat transfer rate is more in CONDUCTORS. AMONG all given optiosn copper is GOOD CONDUCTOR, and HENCE, heat transfer rate will be more in copper.

Discussion

634.	What is the relation between the angle of incidence and the angle of reflection?
Answer» ANSWER :The ANGLE of INCIDENCE is alwaysequal to the angle of REFLECTION.

Discussion

635.	The Earth revolves around the Sun. Does it make Earth a satellite of the Sun?
Answer» ANSWER :No,the EARTH is not a satellite of the Sunbecause a satellite is a celestial body which revolves AROUND a PLANET

Discussion

636.	State whether the following statements are true or false : Sound can travel through solids, liquids and gases.
Answer» ANSWER :A

Discussion

637.	An alloy of copper and zinc weight 320 g in water and 302 g in a liquid of density 1.4 g cm^(-3). If the density of copper is 8.9 g cm^(-3) and that of the zinc is 7.4 g cm^(-3), find the measure of the masses of copper and zinc in the alloy.
Answer» SOLUTION :(i) Give the mass of alloy in water and liquid as `W_(2)` and `W_(3)`. Let the mass of the alloy in air be `W_(1)`. ACCORDING to Archimedes' principle, The density of water `=(W_(1))/(W_(1)-W_(2))` The density of liquid `=(W_(1)xxW_(3))/(W_(1)-W_(2))` From the above equations, find the weight of the alloy in air. Find the volume of the alloy from the weight of the displaced water. Then, the TOTAL volume of copper and zinc is the volume of copper be expressed by `("mass of copper")/("density of copper")` Similary, volume of zinc can be REPLACED by `("mass of zinc")/("density of copper")` `implies (M_(cu))/(8.9)=(M_(zn))/(7.4)` Volume of the alloy. Now, replace `M_(zn)` with (mass of Alloy in air `-M_(cu))` From the above EQUATION, find the masses of copper and zinc present in the alloy. (ii) Maximum density `=5 g cm^(-3)`

Discussion

638.	What are the effects of force?
Answer» ANSWER :When FORCE is APPLIED on an OBJECT, it can MAKE the object.

Discussion

639.	The equatorial meridian of a magnet______
Answer» BISECTS the magnetic axis PERPENDICULARLY is parallel to the magnetic axis makes certain ANGLE with the magnetic equator contains both the poles of the magnet Answer :A

Discussion

640.	Actions like picking, opening, shutting, kicking, hitting, lifting, flicking, pushing, pulling are often used to describe certain tasks. Each of these actions usually results in some kind of change in the motion of an object. Can these terms be replaced with one or more terms?
Answer» ANSWER :YES, these terms can be replaced with ONE or more terms such as push or pull, i.e. FORCE.

Discussion

641.	Fill in the blanks. Sliding friction is _______ than the static friction.
Answer» ANSWER :smaller/lesser

Discussion

642.	Find the mass of the fuel required to raise the temperature of 2 kg of water in a copper containerof mass 1 kg by 88^(@)C. Given calorific value of fuel is 48 MJ kg^(-1), specific heat capacity of water is 1 cal g^(-1).^(@)C^(-1) and specific heat capacity of copper is 0.095 cal g^(-1).^(@)C^(-1).
Answer» Solution :(i) Energy supplied is utilized to RAISE the temperature TURE of both water and container. (ii) Definition of calorific value. (iii) `Q=m_(U)s_(ur)Deltat_(w)+m_(c)s_(c)Deltat_(c)` (iv) Q=mc (V) 16.3 g

Discussion

643.	Define mechanical advantage of a lever.
Answer» always equal to ONE always LESS than one always GREATER than one dependent on where it is held. Solution :A broom stick work as a lever of ORDER three. Hence, its mechanical advantage is less than one.

Discussion

644.	Fill in the blanks in the following. The size of the pupil becomes________when you see in dim light.
Answer» ANSWER :LARGE

Discussion

645.	Define Period of revolution.
Answer» ANSWER :It is the time taken by a planet to complete ONE REVOLUTIONAROUND the SUN.

Discussion

646.	How does sound travel?
Answer» Answer :Sound REQUIRES a medium to travel from ONE place to another. The medium can be solid, LIQUID or gas.

Discussion

647.	Choose the correct option (Multiple choice questions) : 10. Which of the following has large cornea and large pupil to allow more light inits eye?
Answer» Kite Owl Eagle Butterfly Answer :B

Discussion

648.	A sound wave travelling in air is made to propagate through a liquid such that the velocity of sound is quadrupled. If the frequency of the sound wave is constant, find the change in the wavelength of the sound wave
Answer» Solution :(i) When sound moves through different media, will its frequency (n) change ? Find how many times the velocity of sound in are `(V_(1))` increases when made to pass through liquid `(V_(2))` Then, TAKE velocity, WAVELENGTH of sound in air and liquid as `V_(1), lamda_(1), V_(2), lamda_(2)`, respectively Here, `V_(1) = nlamda_(1) and V_(2) = lamda_(2)` (1) Is `V_(2) = 4V_(1)` (2) Substitute (2) in (1) and find the RELATION between `lamda_(1) and lamda_(2)`. Now, find the change in `'lamda', " i.e., " (lamda_(2) - lamda_(1))` (ii) Increase in wave length is thrice the INITIAL wave length

Discussion

649.	What do these examples suggest about the nature of force?
Answer» ANSWER :the nature of FORCE evident from these examples are :(i) if multiple FORCES are APPLIED on an object in the same direction, it adds to one anothert.(II) If two forces act on an object from opposite direction.

Discussion

650.	Fill in the blanks in the following statement. The north pole of a magnet _______ the north pole of another magnet.
Answer» ANSWER :REPELS.

Discussion

Explore topic-wise InterviewSolutions in .

State whether the following statements are true or false : Comets revolve around the Sun in highly elliptical orbits.

Time period of simple pendulum increase with

What is incident ray?

State whether the following statements are true or false : A normal eye can clearly see distant objects as well as objects nearby.

Assertion (A) : When wind blows at a very high speed over the roof of a hut, the roof is blown away. Reason (R ) : The pressure exerted by a fluid at rest is transmitted unchanged equally in all directions.

In the expression buoyant force or upthrust =V xx rho xx g rho is the density of the liquid displaced.

If scientists know so much about earthquakes, can they also predict when and where the next one will strike?

What are plates?

A new scale fo temperature is introduced. One degree temperature difference on the new scale is found to be equal to (5)/(8).^(@)C. Determine the temperature in Celsium scale when the new scale and the celsium scale shows the saer eading. The lower fixed point on the new scale is 33^(@) degree.

Explain why a charged balloon is repelled by another charged balloon whereas an uncharged balloon is attracted by another charged balloon.

Who proved that lightning and spark from clothes are the same phenomena and when?

The loudness of sound of the bell in the bell jar experiment gradually decreases with _____

Fill inthe blanks. Asteroids are found between the orbits of _____ and _______

What do you mean by vacuum?

Each loop of a solenoid acts like a tiny magnet with north and south poles.

The effective length of the magnet shown above is ______.

Now recall what happended when you and your friend pushed the heavy box in the same direction.

What dio you mean by force?

A stone is dropped from the top of a tower and it hits the ground at t = 3.5s. If the velocity of sound in air is 300 ms^(-1), find the time taken to hear the sound by a person on the top of the tower, from the instant the body is dropped (g = 10 ms^(-2))

Explain Action and reaction

Fill in the blanks in the following. Night birds have________ cones than rods in their eyes.

If water be used to construct a barometer, what would be the height of water column at a standard atmospheric presure (76cm of mercury)?

For the range of frequencies of sound 11 kHz to 11 find the time taken by a vibrating particle to move from its mean position to the immediate rarefaction.

What do you mean by noise pollution?

The magnetic compass is not useful for navigation near the magnetic poles because

Suggest three measures to protect ourselves from lightning.

Which one of the following physical quantities increases as we go deep into the sea ?

What can be added to water to make,it more conducting?

It is possible to melt a piece of aluminium placed in a spoon made of zinc.

After doing the electroplating activity. Paheli interchanged the eIectrodes and repeated the activity. What do you think that she would observe this time?

heat transfer rate is more ini_____

What is the relation between the angle of incidence and the angle of reflection?

The Earth revolves around the Sun. Does it make Earth a satellite of the Sun?

State whether the following statements are true or false : Sound can travel through solids, liquids and gases.

An alloy of copper and zinc weight 320 g in water and 302 g in a liquid of density 1.4 g cm^(-3). If the density of copper is 8.9 g cm^(-3) and that of the zinc is 7.4 g cm^(-3), find the measure of the masses of copper and zinc in the alloy.

What are the effects of force?

The equatorial meridian of a magnet______

Actions like picking, opening, shutting, kicking, hitting, lifting, flicking, pushing, pulling are often used to describe certain tasks. Each of these actions usually results in some kind of change in the motion of an object. Can these terms be replaced with one or more terms?

Fill in the blanks. Sliding friction is _______ than the static friction.

Find the mass of the fuel required to raise the temperature of 2 kg of water in a copper containerof mass 1 kg by 88^(@)C. Given calorific value of fuel is 48 MJ kg^(-1), specific heat capacity of water is 1 cal g^(-1).^(@)C^(-1) and specific heat capacity of copper is 0.095 cal g^(-1).^(@)C^(-1).

Define mechanical advantage of a lever.

Fill in the blanks in the following. The size of the pupil becomes________when you see in dim light.

Define Period of revolution.

How does sound travel?

Choose the correct option (Multiple choice questions) : 10. Which of the following has large cornea and large pupil to allow more light inits eye?

A sound wave travelling in air is made to propagate through a liquid such that the velocity of sound is quadrupled. If the frequency of the sound wave is constant, find the change in the wavelength of the sound wave

What do these examples suggest about the nature of force?

Fill in the blanks in the following statement. The north pole of a magnet _______ the north pole of another magnet.

Fill inthe blanks. Asteroids are found between the orbits of _ and ___