Saved Bookmarks
This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.
| 39601. |
Explain the method to find the centre of gravity of irregularly shaped lamina. |
|
Answer» Solution :(i) The center of gravity of a uniform lamina of even an irregular SHAPE is determined by pivoting it at various POINTS by trial and error. (ii) The lamina remains horizontal when pivoted at the point where the net gravitational FORCE acts, which is the center of gravity. (III) When a body is supported at the center of gravity, the sum of the torques acting on all the point masses of the rigid body becomes ZERO. Moreever the weight is compensated by the normal reaction force exerted by the pivot. (iv) The body is in static equilibrium and hence it remains horizontal.  (v) There is also another way to determine the center of gravity of an irregular lamina. If we suspend the lamina from different points like P, Q, R. The vertical lines PP', QQ', RR' all pass through the center of gravity. (vi) Here, reaction force acting at the point of suspension and the gravitational force acting at the center of gravity cancel each other and the torques caused by them also cancel each other. |
|
| 39602. |
Two metallic spheres S_(1) and S_(2) made of same material have identical surface finish. The mass of S_(1) is 3 times that of S_(2). Both are heated to same temperature and are placed in same surroundings. Then ratio of their initial rates of fall of temperature will be |
|
Answer» `(1)/( SQRT3)` |
|
| 39603. |
If vec(P)=2hat(i)+3hat(j)-4hat(k)andvec(Q)=5hat(i)+2hat(j)+4hat(k). Find the angle between the two vectors. |
|
Answer» `30^(@)` |
|
| 39604. |
A sine wave travelling to right is represented by the equation y=asin(kx-omegat).The velocity of the wave is given by |
|
Answer» `k/omega` |
|
| 39605. |
Whyclothes are easily washed by soap or detergent ? |
|
Answer» Solution :The addition of soap detergent in water reduce the angle of contact .the DIRT of matter is enclosed in the clothes . The molecules of detergent are hairpin SHAPE, with one end attracted to water and the other to molecules of grease, oil or wax (dirt), thus TENDING to form water -oil interfaces . the surface TENSION reduces drastically. Hence clothes washes easily. Water PROOFING agent is added for forming large angle of contact between water and fibers. |
|
| 39606. |
While polishing a substance if the polishing cloth is pressed hard a considerable amount of heat is developed. Why ? |
| Answer» SOLUTION :Increase in pressure increases the normal force. Hence force of FRICTION also increases. So, a GREATER AMOUNT of work has to be done against friction while polishing, which in turn generates a a greater amount of HEAT. | |
| 39607. |
A uniform rod AB of mass 'm' length 2a is allowed to fall under gravity with AB in horizontal. When the speed of the rod is 'v', suddenly the end 'A' is fixed. Find the angular velocity with which it begins to rotate . |
|
Answer» Solution :`L_(1)=L_(2)` `mva=Iomega` `mva=(m(2a)^(2))/(3)omegaimpliesomega=(3V)/(4A)` 
|
|
| 39608. |
Two liquids at temperatures 60^@C and 20^@C respectivelyhave masses in the ratio 3:4 and their specific heats in the 4:5 . If the two liquids are mixed , the resultant temperature is |
| Answer» ANSWER :D | |
| 39609. |
What is the direction of the angular velocity of the minute hand of a clock ? |
| Answer» SOLUTION :PERPENDICULAR to the PLANE of the CLOCK | |
| 39610. |
A satellite is in an elliptical orbit around the earth with aphelion of 6R and perihelion of 2R where R = 6400 KM is the radius of the earth. Find the eccentricity of the orbit. |
|
Answer» Solution :We KNOW that Perigee `(r_p) = a(1-e) = 2R...(1)`, APOGEE `(r_a) = a(1 +e) = 6R `..... (2) Solving (1) and (2)`RARR ` we get eccentricity (e) `=1/2` |
|
| 39611. |
A spring is stretched by applying load to its free end. The strain produced in the spring is .......... . |
|
Answer» volumetric |
|
| 39612. |
In which condition a body lying in gravitational field is in stable equilibrium? |
| Answer» Solution :When VERTICAL LINE through CENTRE of gravity PASSES through the base of the BODY | |
| 39613. |
A solid cylinder of mass M and radius .R. is mounted on a frictionless horizontal axle so that it can freely rotate about this axis. A string of negligible mass is wrapped round the cylinder and a body of mass .m. is hung from the string. The mass is released from rest. Find the tension in the string and the angular speed of cylinder as the mass falls a distance h. |
|
Answer» Solution :The ACCELERATION .a. of the falling body is given by `mg-T=ma ""`……(1) Torque on the cylinder is `tau = TR = I alpha` `therefore T=(I alpha)/(R )=((MR^(2))/(2))((a)/(R^(2))) "" [because alpha = (a)/(R )]` or `T=(Ma)/(2)`.....(2) from (1) and (2) `T=(mMg)/((M+2m))` from CONSEVATION of energy, we have `mgh = (1)/(2)mv^(2)+(1)/(2)I omega^(2)` `=(1)/(2)m (Romega)^(2)+(1)/(2)((MR^(2))/(2)).omega^(2)` on solving `omega = [(4mgh)/((M+2m)R^(2))]^((1)/(2))` 
|
|
| 39614. |
Two perfectly elastic balls of same mass m are moving with velocities u_(1)" and "u_(2). They collide elastically n times. The kinetic energy of the system finally is |
|
Answer» `(1)/(2) (m)/(n) u_(1)^(2)` |
|
| 39615. |
Rain is falling vertically with a speed of 30 ms^(-1). A woman rides a bicycle with a speed of 12 ms^(-1) in east to west direction. In which direction she should hold her umbrella ? |
|
Answer» At an ANGLE of `tan^(-1)((2)/(5))` with the VERTICAL TOWARDS the east. |
|
| 39616. |
The moment of inertial of an uniform circular disc about its central axis I 'I' . Its M.I about a tangent in its plane is equal to |
| Answer» ANSWER :B | |
| 39618. |
The acceleration due to gravity on the planet. A is 9 times the acceleration due to the gravity on planet B. A man Jumps to a height of 2m on the surface of A. What is the height of jump by the same person on the planet B ? |
|
Answer» `2/3m` Kinetic energy of planet = Potential energy For planet A : `1/2 mv_A^2 = mg_(A) h_A ` For planet B: `1/2 mv_B^2 = mg_Bh_B` Suppose both planets having same orbital velocity `v_A =v_B implies1/2 mv_A^2 =1/2 mv_B^2` `:. g_A h_A = mg_B h_B` `:. h_B = (g_A) /(g_B) h_A` `= ((9g_B)/(g_B)) XX 2` `= 9xx 2 = 18 m` |
|
| 39619. |
Explain why a high pressure tyre roll more easily than a low pressure tyre ? |
| Answer» SOLUTION :AREA of CONTACT is less for high pressure TYRE. | |
| 39620. |
A hollow metal sphere is filled with water and it is hung by along thread. It is made to oscillate. If there be a small hole in the bottom through which water slowly flows out. Then its period of oscillation is |
|
Answer» goes on INCREASING until the sphere is empty |
|
| 39621. |
A ring is cut from a platinum tube having 10 cm internal and 11 cm external diameter. It is supported horizontally from a pan of balance, so that it comes in contact with water in a glass vessel. What is the surface tension of water if an extra, 4.752gwt is required to pull it away from water ? (g=10m//s^2) |
|
Answer» `7.2 xx 10^(-2) "N/m"` |
|
| 39622. |
A ball bounces to 80% of its original height. What fraction of its mechanical energy is lost in each bounce ? What other form does it take ? |
|
Answer» |
|
| 39623. |
If M is the magnetic moment, B is the magnetic induction and T is the time then MBT^(2) has the dimensions of |
|
Answer» INTENSITY of magnetization |
|
| 39624. |
Definespectificheat capacity and giveits unit . |
|
Answer» Solution :SPECIFIC HEAT capacity of a substance is defined as the amount of heat energy REQUIRED to raise the TEMPERATURE of 1 kg of a substance by 1 KELVIN or `1^(@)C` `""DeltaQ=msDeltaT` `"Therefore,"s=(1)/(m)((DeltaQ)/(DeltaT))` The SI unit for specific heat capacity is `"J kg"^(-1)K^(-1)` |
|
| 39625. |
A glass tube of uniform area of cross section and open at one end encloses some air at 27^@C by a 4 cm long mercury thread that acts like a piston. When the tube is held vertical with its open end up length of the air column in the tube is 9 cm.When the open end is held downwards by turning the tube,the length of the enclosed air column becomes 10 cm. Find () the value of the atmospheric pressure (ii) the temperature at which the length of the air column becomes 9cm again,while the tube is still held inverted. |
Answer» SOLUTION :Let the ATMOSPHERIC pressure =pcmHg and the area of cross section of the tube =`a cm^2`[Fig.6.10] when the open end is kept upwards the VOLUME of the confined air `V_1=9 a cm^3` and pressure `p_1=(p+4) cmHg`.  On INVERTING the tube volume of the confined air `V_2=10 a cm^3` and pressure `p_2(p-4)`cmHg. Assuming temperature to be constant at `27^@C` from Boyle.s law `p_1V_1=p_2V_2` or,`9a(p+4)=10a(p-4)` or,`9p+36=10p-40 , or p=76 cmHg` Suppose at `T_2K` the length of the air column becomes 9 cm again when the tube is still held inverted.Then it pressure `p_2=76-4=72 cmHg` and volume `V_2=9a cm^3`. `therefore(p_1V_1)/T_1=(p_2V_2)/T_2` or,`((76+4)times9a)/(273+27)=(72times9a)/T_2or,80/300=72/T_2` `thereforeT_2=270K=(270-273)^@C=-3^@C` |
|
| 39626. |
The temperature of a piece of iron is 27^(@)C and it is radiating energy atthe rate of QkWm^(-2). If its temperature is raised to 151^(@)C, the rate of radiation of energy will become approximately |
|
Answer» `2QkWm^(-2)` |
|
| 39627. |
Two identical bodies at temperature T_(1) and T_(2) are bought into thermal contact. Under what conditios they come to thermal equilibrium at the mean temperature. |
|
Answer» |
|
| 39628. |
An artificial,satellite of mass .m. is revolving around the earth, in a circular orbit of radius .r.. If the mass of the earth is.m. angular momentum of the satellite with respect to the centre of earth is (G-universal gravitational constant): |
|
Answer» `sqrt(GMm^(2)r)` |
|
| 39629. |
Aparticle moves with an initial velocity V_(0) and retardation beta V. Where 'V' is it's velocity at any time 't' ( beta is +ve constant) |
|
Answer» The PARTICLE will cover a total distance of `(V_(0))/(beta)` |
|
| 39630. |
The piston in the cylinder head of a locomotive has a stroke (twice the amplitude) of 1.0 m. If the piston moves with simple harmonic motion with an angular frequency of 200 rad/min, what is its maximum speed ? |
|
Answer» Solution :AMPLITUDE of piston `A= (1)/(2) CM= 0.5 cm` and angular frequency `omega = 200 rad"/"min` Maximum SPEED of piston execute SHM, `v= A omega` `THEREFORE v= 0.5 xx 200` `= 100 cm"/"min = (100)/(60) = 1.67 cms^(-1)`. |
|
| 39631. |
In a streamline flow, (i) the speed of a particle always remains same (ii) the velocity of a particle always remains same (iii) the kinetic energies of all the particles arriving at a given point are the same (iv) the momenta of all the particles arriving at a given point are the same. |
|
Answer» (i),(III) |
|
| 39632. |
A Styrofoam box, used to keep drinks cold at a picnic, has total wall area (including the lid) of 0.8m^(2) and wall thickness 2 cm. It is filled with ice, water and coca-cola at 0^(0)C. What is the rate of heat flow between the box and the surrounding and in which direction it is flowing ? Take atmospheric temperature as 30^(0)C. Thermal conductivity of Styrofoam is 0.01 W/m-K. |
|
Answer» 12 W, Out of BOX |
|
| 39633. |
The initial state of a certain gas is (P_i,V_i,T_i). It undergoes expansion till its volume becomes V_f Consider the following two cases : (a) the expansion takes place at constant temperature. (b) the expansion takes place at constant pressure. Plot the P-V diagram for each case. In which of the two cases, is the work done by the gas more ? |
Answer» Solution :The situation is shown in the GIVEN P `to`V graph where variation is shown for each PROCESS.  Process 1 is isobaric and process 2 is isothermal. SINCE work done is EQUAL to the area under the P`to`V CURVE, here area under the P `to`V curve 1 is more, so work done is more in isobaric process. |
|
| 39634. |
The ratio of SI unit to CGS unit of a physical constant is 10^(7). The constant is |
|
Answer» UNIVERSAL GAS constant |
|
| 39635. |
(A) : A quick collision between two bodies is more violent 6than slow collision, even when initial and final velocities are identical.(R ) : The rate of change of momentum which determines the force is greater in quick collision. |
|
Answer» Both (A) and (R ) are TRUE and (R ) is the correct explanation of (A) |
|
| 39636. |
Why do the blades of an electric fan continue to ratatefor some timeafter thecurrent is switched off |
| Answer» SOLUTION :THISIS DUETO inertiamotionthat THEBLADES of an electricfancontinue to rotateforsometimeevenafterthe fanhasbeenswitchedoff. | |
| 39637. |
A mass of 2kg attached to a spring of force constant 260 Nm^(-1)makes 100 oscillation. What is the time taken ? |
|
Answer» Solution :MASS attached on = 2KG , Force CONSTANT k= 260 N/m `therefore T= 2 xx 3.142xx 0.0877 = 0.551 ` SEC Time for 100 OSCILLATION `=100 xx 0.551 = 55.1 ` sec. |
|
| 39638. |
A uniform steel rod of length 1m and area of cross section 20 cm^2is hanging from a fixed support. Find the increase in the length of the rod. |
|
Answer» `1.923xx10^(-5)CM` |
|
| 39639. |
A spherical shell of copper is completely filled with a liquid at a temperature t°C. The bulk modulus of the liquid is K and coefficient of volume expansion is gamma. If the temperature of the liquid and the shell is increased by DeltaT. then the outward pressure Delta P on the shell that results from the temperature increase is given by ( alpha is the coefficient of linear expansion of the material of the shell) : |
|
Answer» `K ( gamma - 3alpha) Delta T` |
|
| 39640. |
Identify the pair which has different dimensions |
|
Answer» PLANCK's constatnt and ANGULAR MOMEMTUM |
|
| 39641. |
A 400 kg satellite is in a circular orbit of radius 2 R_(E)about the Earth. How much energy is required to transfer it to a circular orbit of radius 4R_(E) ? What are the changes in the kinetic and potential energies ? |
|
Answer» Solution :Inttlally, `E_(1) =- (GM_(E)m)/(4R_(E))` whtle finally `E_(f) = - (GM_(E)m)/(8 R_(E))` The change in the total energy is `Delta E = E_(f) - E_(i)` `=(GM_(E)m)/(8 R_(E)) = ((GM_(E))/(R_(E)^(2))) (mR_(E))/(8)` `Delta E = (gmR_(E))/(8) = (9.81 xx 400 xx 6.37 xx 10^(6))/(8) = 3.13 xx 10^(9)` J Thekinetic energy is reduced and it mimics `Delta`E, namely ,` Delta K = K_(f) - K_(i) = - 3.13 xx 10^(9) J. ` The change in POTENTIAL energy is twice the change n the total energy , namely `Delta V = V_(f) - V_(i) = - 6.25 xx 10^(9) `J |
|
| 39642. |
Sudeep and Karthideyan were roommates. Sudeepwasboilingwater in avessel forbathing purpose. KarthikeyansaidSudeep , you knowwhenyou touchthe middlepartofthe vesselcontainingwater you can feellessheat thanwhat youcan feelat the top. Sudeepwasshockedto hear.Karthikeyantook athermometerand keptit at the topsurfaceof water. The temepaturewas rising.Againheinsertedit deep into the vesselcontainingwater , now thetemperaturehas fallen downthan in the previouscondition.Whatis tehtruthbehind it ? (i) It is good to keepourhanddeep intothe vesselto checkthiswhilethe liquid is boiling ? , (ii)Whatare convectioncurrent ? |
|
Answer» Solution :The truthbehindthismagicis convectionprocess. It is a phenomenonof heattransfer in a fluid withthe actual movementof the particlesof the flud .i.e.,WHENA fluidis heatedthe hotpartexpandsandbecomeslessdense , so itrisesup andreplacesthe colderpartof fluid. Againthis fluidis heatedrisesup of replacesthe colderpartof thefluid. Thisprocessgoeson . THATIS whywhenweboilwaterheatwillbe from TOP layer of the liquid to thebottomlayer. (i)No,it is notgoodtochecklike this.Asthe toplayerof fluid is not,ourhandsmustcrossthislayerfirstto moveitdeepintothe veseelcontainingwatter.so youmaygetburnsorswells. (II) Convectioncurrentsare the constantcyclicalmotionof airwaterandothersubstanceto distributeheat . Asheatedairrises,forexampleit pullscoolerair intoitsplacewhereit can be heatedriseandpull in mostcoll air.Somegeologistsbelieveconvectioncurrentswithinthe Earth'smoltenrocks (insemi-liquid STATE)are a contributingcause ofvolcanoeseqrthquakes andcontinentaldrift. |
|
| 39643. |
A simple pendulum with a bob of mass m oscillates from A to C and back to such that PB is H. If the acceleration due to gravity is g, then the velocity of the bob as it passes through B is……….. |
|
Answer» `mgH` `mgH= (1)/(2) mv^(2) IMPLIES v= sqrt(2gH)` 
|
|
| 39644. |
Steam at 100°C is passed into 22 grams of water at 20°C. When resultant temperature is 90°C, then weight of the water present is |
|
Answer» 27.33g |
|
| 39645. |
Underline the correct alternative : The rate of change of total momentum of a many-particle system is proportional to the external force/sum of the internal forces on the system. |
| Answer» SOLUTION :EXTERNAL FORCE | |
| 39646. |
A body dropped from a height h into the floor makes elastic collision with the floor. The frequency of oscillation of its periodic motion is |
|
Answer» `(1)/(2)SQRT((g)/(2H))` |
|
| 39647. |
The angular momentum of a wheel changes from 2L to 5L in 3 seconds. What will be the magnitude of torque acting on it? |
| Answer» Solution :`tau=(DL)/(DT)=(L_(2)-L_(1))/(3)=(5L-2L)/(3)=(3L)/(3)=L` | |
| 39648. |
The following photographs are taken from the recent lunar eclipse which occurred on January 31, 2018. Is it possible to prove that Earth is a sphere from these photographs? |
| Answer» SOLUTION :No. The MOON GOES aroud the earth in an elliptical orbit. This means it goes around US. | |
| 39649. |
A bucket filled with water having a mass of 15kg is raised from a well of depth 12m with the help of a rope. If the work done to do so is 2160J, the linear density of the rope is (g=10ms^(-2)) |
|
Answer» 0.2kg/m |
|
| 39650. |
A particle executing SHM crosses points A and B with the same velocity . Having taken 3 s in passing from A to B , it returns to B after another3 s . The time period is |
|
Answer» 15 s |
|