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1001.

The value of acceleration due to gravity of earth :

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is the same on equator and POLES
is the LEAST on poles
is the least on equator
INCREASE from POLE to equator

Answer :C
Discussion
1002.

A hollow metallic sphere is heated. Explain in the type of change produced in its (a) internal radius (b) external radius (c) volume (d) mass (e) density

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SOLUTION :(i) Take volumes of the body at `t_(1)""^(@)C" and "t_(2)""^(@)C` be `V_(1)" and V_(2),` respectively. Take the DENSITIES of the liquid at `t_(1)""^(@)C" and "t_(2)""^(@)C" as "d_(1)" and "d_(2)`, respectively. Find the apparent loss in weight of the body in liquid at `t_(1)""^(@)C" and "t_(2)""^(@)C.`
`W_(1)-W_(2)=V_(1)d_(1)g`
`"and"W_(1)-W_(3)=V_(2)d_(2)g`
The volume coefficient of the solid body
`=gamma=(DeltaV)/(V_(0)DeltaT)=(V_(2)-V_(1))/(V_(1)(t_(2)-t_(1)))""^(@)C^(-1)`
Convert `V_(1) and V_(2)` in terms of `W_(1),W_(2),g,d_(1) and d_(2)` SUBSTITUE it in above equation and obtain REQUIRED solution.
(ii) `(d_(1)(w_(1)-w_(3))-d_(2)(w_(1)-w_(2)))/(d_(2)(t_(2)-t_(1))(w_(1)-w_(2)))""^(@)C^(-1)`
Discussion
1003.

A lift carries a maximum weight of 2400 N to a height of 10 m with a constant speed 2ms^(-1). Find out the power and the work done.

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Solution :Here, weight = force = `2400 N, h=10M,` speed = `2MS^(-1)`
Work done = `Fs=Fh=2400 Nxx10m`
`=24000J`
Speed = `("Distance")/("Time")`
`THEREFORE` Time = `("Distance")/("Speed")=(10m)/(2ms^(-1))=5s`
Power = `("Work")/("Time")=(24000J)/(5s)=4800W`
Discussion
1004.

A bus decreases its speed from 80 km h^(-1) to 60 km h^(-1) in 5s. Find the acceleration of the bus.

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Solution :Initial speed of the bus `(u) = 80 km h ^(-1)`
`= ( 80 XX 1000)/( 3600) ms ^(-1)`
`= (800)/(36) ms ^(-1)`
FINAL speed of the bus `(v) =60 kmh^(1)`
`= (60 xx 1000)/( 3600) ms ^(-1)`
`= (600)/(36) ms ^(-1)`
Acceleration `= (u-v)/(t) = ((600)/(36)- (800)/(36))/( 5) = (-200)/( 36) xx 1/5 =- (10)/(9) ~~-1.11 ms ^(-2)`
The acceleration of the bus is `-1.11 ms ^(-2)`
`(or -1.11 ms ^(-2))`
Discussion
1005.

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

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ANSWER :`"A:B"" B:a"" C:d""D:e"" E:g""F:c""G:f" "H:j""I:i""J:h"`
Discussion
1006.

Abdul, while driving to school, computes the average speed for his trip to be 20 km h^(-1). On his return trip along the same route, there is less traffic and the average speed is 30 km h^(-1). What is the average speed for Abdul's trip?

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Solution :Let the DISTANCE of school be x km from house of Abdul.
While driving to school,
Average speed `= ("Distance")/("Time")`
`therefore` Time `= ("Distance")/("Average speed")`
`= (x km)/(20 km h ^(-1))`
`= (x)/(20) h ""…(1)`
On return TRIP,
Average speed `= ("Distance")/("Time")`
`therefore` Time `= ("Distance")/("Average speed")`
`= (xkm)/(30 km h ^(-1))` |
`= (x)/(30) h ""...(2)`
Total distance `= (x + x) km = 2 xkm.`
Total time `= ((x )/(20) + (x)/(30)) h `
`= (3X + 2x )/( 60) h`
`= (5x)/(60) h = (x)/(12) h`
Average speed `= ("Total distance")/("Total time")`
`= (2x km)/(x//12 h)`
`= (2x)/(x) XX 12 km h ^(-1) = 24 km h ^(-1)`
The average speed for Abdul.s trip is `24 km h ^(-1).`
Discussion
1007.

Calculate the molality of ZnCl_(2) in a solution prepared by dissolving 4.11 g ZnCl_(2)in 150 g of water.

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SOLUTION :0.201 MOL `KG^(-1)`.
Discussion
1008.

Velocity of a moving car goes on increasing with time. In which direction would the acceleration of this car be?

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in DIRECTION of velocity
in OPPOSITE direction to velocity
in PERPENDICULAR direction to velocity
in any direction

Answer :A
Discussion
1009.

Analyse the graphs given below. Which graph indicates non uniform velocity?

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ANSWER :GRAPH (4)
Discussion
1010.

Weighing a stone of lower mass and another of higher mass by using a spring balance. [Mass of a body is the amount of matter contained in it] On the basis of these observations, find out the factor that influences the force of attraction from the earth.

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ANSWER :The FACTOR is MASS
• As the distance between the bodies increases gravitational force decreases
• ANOTHER factor which influences the gravitationalforce is distance between the objects.
Discussion
1011.

Weighing a stone of lower mass and another of higher mass by using a spring balance. [Mass of a body is the amount of matter contained in it] In which case was the reading higher?

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Answer :READING of the spring BALANCE is higher when the STONE having greater MASS is weighed.
Discussion
1012.

Weighing a stone of lower mass and another of higher mass by using a spring balance. [Mass of a body is the amount of matter contained in it] Which of the stones experienced greater force of attraction of the earth?

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Answer :Greater FORCE of attraction of the EARTH is EXPERIENCED in stone having greater MASS.
Discussion
1013.

How will you find the thickness of a one rupee coin ?

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SOLUTION :(i)Determine the pitch, the LEAST count and the zero error of the screw gauge
(ii)Place the coin between the two studs
(iii)Rotate the head untilthe coin is held FIRMLY but not tightly, with the help of the ratchat
(iv)Note the reading of the pitch scale crossed by the head scale (PSR) and the head scale DIVISION that coincides with the pitch scale axis (HSC)
(iv)The width of the coin is given by PSR + CHSR (Corrected HSR) . Repeat the experiment fordifferent positions of the coin
(vi)Tabulate the reading
(vii)The average of the last column reading gives the width of the coin
Thickness of the coin = . . . . . . m m
Discussion
1014.

A man standing at a point on the line joining the feet of two cliffs fires a bullet . If he hears the 1^(st) echo after 4 seconds and the next after 6 seconds , then what is the distance between the two cliffs ? (Take the velocity of sound in air as 330 m s^(-1))

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SOLUTION :(i) `V = (2d)/(t)`
(ii) Apply the FORMULA d = Vt for both the cliffs.
Then add the TWO distances to get the DISTANCE between the two cliffs.
(III) 1650 or 1.65 km .
Discussion
1015.

If you place your ear close to an iron railing which is tapped some distance away, you hear the sound twice. Explain why?

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Solution :SOUND travels in iron FASTER than in air, so first the sound through iron RAIL is HEARD and then the sound through air is heard.
Discussion
1016.

A car travels a distance 50 km with a velocity 25 km h^(-1) and then 60 km with a velocity 20 km h^(-1) in the same direction. Calculate : (i) the total time of journey and (ii) the average velocity of the car.

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Solution :Given `S_(1)= 50 ` km `v_(1)` 25 km `H^(-1)`.
`S_(2)= 60 ` km , `V_(2)= 20` km `h^(-1)` .
(i) Time of journey t `= ("Distance S")/("velocity v")`
`:. T_(1) = (S_(1))/(v_(1))= (50 km)/(25 km h^(-1))= 2 `h
`t_(2)= (S_(2))/(v_(2))= (60 km)/(20 km h^(-1))=3 `h
Total time of journey t = `t_(1)+t_(2)`= 2h +3 h = 5 h
(II) Total distance travelled `S=S_(1)+S_(2)`
= 50 km + 60 km = 110 km
Average velocity = `("Total distance travelled S")/("Total time of journey t ") `
`= (110km )/(5 h)` = 22 km `h^(-1)`.
Discussion
1017.

Explain with diagrams how refraction of incident light takes place fromrarer to denser medium

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Solution :rarer to denser MEDIUM:
When a ray of LIGHT TRAVELS from optically rarer medium to optically denser medium, it bends towards the normal.

Discussion
1018.

In thespeed-time graph for a moving object shown here, the part which indicates uniform deceleration of the object is :

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AB
BC
CD
DE

Answer :C
Discussion
1019.

How are the potential difference (V), current (I) and resistance (R) related ?

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ANSWER :`V = IR`
Discussion
1020.

A stationary object, when starts motion, covers 20 m distance in first 28 and 160 m in next 4 second. Calculate the velocity at the end 7 second from the beginning of the motion.

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SOLUTION :`70 MS ^(-1)`
Discussion
1021.

{:(,"Column I",,"Column II"),(,("Physical Quantity"),,("Formula")),(1.,"Work",a.,(W)/(t)),(2.,"Power",b.,mgh),(3.,"Potential energy",c.,(1)/(2)mv^(2)),(4.,"Kinetic energy",d.,Fs),(,,e.,ma),(,,,):}

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ANSWER :(1-d), (2-a), (3-b), (4-c).
Discussion
1022.

A body of mass 'm' is kept on the horizontal floor and it is pushed in the horizontal direction with a force of 10N continuously, so that it moves steadily. (a) Draw FBD (a diagram showing all the forces acting on the body at a point of time) (b) What is the value of friction ?

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Solution :
Given tht the body is moving steadily, Hence the net force on the body is zero both in horizontal and vertical DIRECTIONS. Forces acting on it along horizontal direction are force of friction (F), force of PUSH (F)
We KNOW the `f _(n et,x) =0`
`F + (-f) =0`
`F =f`
Hence the vlaue of force of friction is 10N.
Discussion
1023.

Potassium super oxide, KO_(2) is an air purifier as it eacts with CO_(2) and releases O_(2),4KO_(2)(s)+2CO_(2)(g) to 2K_(2)CO_(3)(s)+3O_(2)(g) Calculate the mass of KO_(2) neeeded to react with 50 L of CO_(2) at 25^(@)C, 1 atm.

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Solution :STRATEGY: * Find `V_(m)` at given (T,P) * USE `n=(V)/(V_(m))` to find n of `CO_(2)`.
* Use `m_(KO_(2))=n_(KO_(2)):` * `n_(KO_(2))` is obtained from stoichiometry.
* `V_(m)(CO_(2))=(RT)/(P)=0.0821xx298.15//1L=24.47" L "mol^(-1)`: * `n_(CO_(2))=(V)/(V_(m))=(50L)/(24.47" L "mol^(-1))=2.043` mole
* From stoichiometry, 2 mol `CO_(2)` reacts with 4 mol `KO_(2)therefore n_(KO_(2))=(4)/(2)xxn_(CO_(2))=2xx2.043` mol =4.086 mol
* FINALLY use m=nM or, `m_(KO_(2))=4.086molxx71.1g" "mol^(-1)=290.56g`
Discussion
1024.

Define 1 watt of power.

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Solution :The power of an agent (DEVICE or an appliance) is one WATT, if it does WORK at the rate of 1 joule per second.
Discussion
1025.

A stone falls down from the top of a wall in 1 s to the ground (g=10 m/s^2) Calculate the average speed when the stone is falling down

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Answer :`Average speed = frac(TOTAL DISTANCE)(Total TIME)`
`Total distance=S=ut+1/2at^2`
`=0xx1+1/2xx10xx1^2`
=5M
`Average speed=5/1=5m/s`
Discussion
1026.

Explain the discharge tube phenomenon and give an account of the observation at various pressures.

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Discussion
1027.

The weight of a piece of stone in air 120 N and its weight in water is 100 N. Calculate the buoyancy, experienced by the stone.

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ANSWER :Buoyancy=weight of STONE in air-weight in WATER`=120 N-100 N``=20 N`
Discussion
1028.

Sound is a …………….. Wave and needs a material medium to travel.

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ANSWER :LONGITUDINAL
Discussion
1029.

What is mechanical energy?

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SOLUTION :The sum of kinetic ENERGY and POTENTIAL energy is MECHANICAL energy.
Discussion
1030.

The principle used in the construction of air (gas) thermometer is

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VARIATION of volume with temperature at constant PRESSURE.
variation of volume with temperature at constant HEAT energy.
variation of pressure with temperature at constant volume
variation of pressure with temperature at constant heat energy

Solution :The pressure exerted on the air thermometer is 1 atm and the volume of the air CHANGES with temperature.
Discussion
1031.

Define buoyant force. Name two factor on which bouyant force depens. What is the cause of buoyant force ?

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ANSWER :( C) 6000 N
Discussion
1032.

The fundamental unit is :

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NEWTON
pascal
hertz
SECOND

Solution :second
Discussion
1033.

What is motion ?

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SOLUTION :An object is said to be in motion when its position CHANGES with time with RESPECT to its SURROUNDINGS.
Discussion
1034.

Which of the following unit is not a fundamental unit:

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METRE
LITRE
second
kilogram

Solution :litre
Discussion
1035.

Fill in the blanks :- The water stored in an overhead tank possesses ……………

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SOLUTION :POTENTIAL ENERGY
Discussion
1036.

The mass of a block made of certain material is 13.5 kg and its volume is 15 xx 10^(-3) m^3. Calculate upthrust on the block if it is held fully immersed in water.

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Answer :a. 15 kgf. B. The block will float since upthrust on it when FULLY IMMERSED in water, is more than its weight. C. While FLOATING, upthrust =13.5 kgf.
Discussion
1037.

Why do we use the first gear to start a car or scooter at rest ? Whatwould happen if we started a car/scooter in a higher gear?

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SOLUTION :(i) CONSIDER the FORCES REQUIRED to move avehicle (i) at rest (ii) moving at uniformvelocity.
(ii) In the 1st gear of thevehicle, thedriven gear hasmore number of turns than thedriving gear.
(iii) Gain in torque
`= ("number of turns in driven gear")/("number of turns in driving gear")`
(iv) The car at rest has to overcome INERTIA and static frictionwhich requiresa large torque.
Discussion
1038.

What are wave length, frequency, time period and amplification of a sound wave ?

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Solution :Wave length : The distance betweentwo consecutivecompression or twoconsecutiverarefraction is known as wave length .
Its SI UNIT is meter (cm)
Frequency : The number of complete oscillation PER sound is known as the frequency of a sound wave. It is measure is HERTZ (HZ).
Amplitude : The maximum height reachedby the CREST or through of a sound wave is called its amplitude.
Discussion
1039.

Stand before the mirror in your dressing table or the mirror fixed in a steel almirah. Do you see your whole body?

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Solution :To see your ENTIRE body in a MIRROR, the mirror should be at LEAST HALF of your height.
Height of the mirror = Your height/2.
Discussion
1040.

Does sound follow the same laws of reflection as light does ? How .

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Solution :YES ANGLE of incidence and angle of reflection OBEYS the LAWS.
Discussion
1041.

Water stored in the dam ………..

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does not POSSESS energy
possesses ELECTRICAL energy
possesses KINETIC energy
possesses POTENTIAL energy

Answer :A
Discussion
1042.

{:("Column - I ","Column - II "),("(a) Length","(i) Kelvin"),("(b) Mass","(ii) metre"),("(c) Time","(iii) kilogram"),("(d) Temperature","(iv) second"):}

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Answer :(a) (II)(B) (iii)(C) (IV)(d) (i)
Discussion
1043.

Two dams form artificial lakes of equal depth. However, one lake backs up 15 km behind the dam, and the other backs up 50 km behind. What effect does the difference in lengths have on the pressure on the dams?

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SOLUTION :The PRESSURE is DETERMINED by DEPTH only. So the EFFECT is none-same depth, same pressure.
Discussion
1044.

A body is falling freely from a height h. When it covers distance (h)/(2) in downward direction, at that place it possesses.

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only potential ENERGY
only kinetic energy
HALF potential energy and half kinetic energy
more kinetic energy and less potential energy

ANSWER :C
Discussion
1045.

A girl of mass 35 kg is sitting in a trolley of mass 5 kg. By applying the force on the trolley, it has given the velocity 4ms^(-1). Trolley comes to rest after covering the distance 16 m, then (1) How much work is done on the trolley? (2) How much work is done on the girl?

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Answer :(1) 320 J (2) 0
Discussion
1046.

Define thrust ?

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Solution :The NET force exerted by a body in a PARTICULAR DIRECTION is called thrust.
Discussion
1047.

________ is the modified form of an inclined plane.

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ANSWER :SCREW
Discussion
1048.

An object of mass 1 kg is raised through a height h. Its potential energy increased by 1 joule. Find the height h.

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Solution :MASS : m - 1 kg, height = hm
PE = mgh, TAKING g = `10 m/s^(2)`
PE = (10h)J
now potential energy increases by 1 JOULE
`PE^(1) = (10h + 1)` Joule
`PE^(1)` = mgh 1 = ( 10h + 1)
`10h^(1)` = (10 h + 1)
10 `(h^(1) - h) = 1`
`(h^(1) - h) = 1/10`. If body is on the GROUND h = 0 then `h^(1) = 0.1` m
Discussion
1049.

What is the difference between electromagnetic force and potential difference?

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SOLUTION :The e.m.f. REFERS to the voltage developed across the terminals of an electrical source when it does not produce crrent in the circuit.
Potential difference refers to the voltage develped between any two POINTS in an electric circuit when there is current in the circuit.
Discussion
1050.

A medium should posses the property of "________" for the propagation of mechanical waves .

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PERMEABILITY
inertia
ELASTICITY
both (B) and (c)

Answer :D
Discussion