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InterviewSolution
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.
| 201. |
The following four wires of length L and radius r are made of the same material. Which of these will have the largest extension, when the same tension is applied?A. L = 100 cm, r = 0.2 cmB. L = 200 cm, r = 0.4 cmC. L = 300 cm, r = 0.6 cmD. L = 400 cm, r = 0.8 cm |
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Answer» Correct Answer - a Extension of wire, `e = (FL)/(AY)` `e = (FL)/(pi r^(2) Y)` F and Y are same for all wire, `:. E prop (L)/(r^(2))` `e_(a) = (100)/(0.2 xx 0.2) = 2500` and `e_(b) = (200)/(0.4 xx 0.4) = 1250` e_(c ) = (300)/(0.6 xx 0.6) = 833.34` and `e_(d) = (400)/(0.8 xx 0.8) = 625` We cansee that, first wire have the largest extension |
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| 202. |
There are two wires of same material and same length while the diameter of second wire is 2 times the diameter of first wire, then ratio of extension produced in the wires by applying same load will beA. `1:1`B. `2:1`C. `1:2`D. `4:1` |
Answer» Correct Answer - DBoth wires are same materials so both will have same Young's modulus, and let it be
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| 203. |
When a metal sphere is suspended at the end of a metal wire, its extension is 0.4 mm. If another metal sphere of the same material with its radius is half of the previous, is suspended then extension would beA. 0.05 mmB. 0.02 mmC. 0.01 mmD. 0.32 mm |
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Answer» Correct Answer - A `l_(1) prop m_(1), l_(2) prop m_(2)` `(l_(2))/(l_(1))=(m_(2))/(m_(1))=(rho v_(2))/(rho v_(1)) =((4pi)/(3) r_(2)^(3))/((4pi)/(3)r_(1)^(3))` `(l_(2))/(l_(1)) =((r_(2))/(r_(1)))^(3) =(((r )/(2))/(r ))^(3)=(1)/(8)` `l_(2)=(l_(1))/(8) =(0.4)/(8) =0.05` mm. |
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| 204. |
On mixing impurities, the elasticity of a materialA. decreasesB. increasesC. sometimes increases and sometimes decreasesD. remains same |
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Answer» Correct Answer - B `y=("stress")/("strain") therefore "strain"=(10^(9))/(2xx10^(11)) =0.5 xx10^(-2)` `therefore (Delta r)/(r ) = 0.5 xx10^(-2)` `therefore Delta r = 2.8 xx 0.5 xx 10^(-2) = 14 xx 10^(-3) A^(@)`. |
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| 205. |
The work done by surface tension on rising water do height of `h` in a capillary tube of radius `r` isA. `(2pi T^(2))/(rho g)`B. `(rho g)/(2pi T^(2))`C. `(pi T^(2))/(rho g)`D. `(2pi T^(2))/(rho)` |
| Answer» Correct Answer - A | |
| 206. |
The length of a wire `l_(1)` when tension is 4 N and `l_(2)` when the tension is 5 N. Then its original length would beA. `9l_(1)-8l_(2)`B. `5l_(1)+4l_(2)`C. `5l_(1)-4l_(2)`D. `9l_(2)-8l_(1)` |
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Answer» Correct Answer - B `L=(T_(2)l_(1)-T_(1)l_(2))/(T_(2)-T_(1))` `=(5l_(1)-4l_(2))/(5-4)=5l_(1)-4l_(2)`. |
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| 207. |
One end of a uniform wire of length `l` and weight W is attached to a point in the roof and a weight W/2 is suspended from the lower end. If A is the area fo cross-section of the wire, then stress of the wire at its midpoint will beA. `(W)/(2A)`B. `(2W)/(A)`C. `(3W)/(2A)`D. `(W)/(A)` |
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Answer» Correct Answer - D Stress `=(F)/(A)` `F=(W)/(2)+(W)/(2)=W` Stress `=(W)/(A)`. |
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| 208. |
When the tension in a metal wire is `T_(1)`, its length is `I_(1)`. When the tension is `T_(2)`, its length is `I_(2)`. The natural length of wire isA. `sqrt(l_(1)l_(2)`B. `(l_(1)+l_(2))/(2)`C. `((l_(1)T_(2)-l_(2)T_(1)))/(T_(2)-T_(1))`D. `(l_(1)T_(2)-l_(1)T_(2))/(T_(1)-T_(2))` |
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Answer» Correct Answer - C Let unstrethched length = I `T_(1)=K(l_(1)- l) rArr T_(2)= k(l_(1)-l)` `(T_(1))/(T_(2))= (l_(1)-l)/(l_(2)-l) rArrl= ((T_(2)l_(1)-T_(1)l_(2))/(T_(2)- T_(2)))` |
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| 209. |
The length of a metal wire is `l_(1)` when the tension in it is `T_(1)` and is `l_(2)` when the tension is `T_(2)`. Then natural length of the wire isA. `((l_(1)+l_(2)))/(2)`B. `((l_(1)-l_(2)))/(2)`C. `(l_(1)T_(2)-l_(2)T_(1))/(T_(2)-T_(1))`D. `(l_(1)T_(2)+l_(2)T_(1))/(T_(2)+T_(1))` |
| Answer» Correct Answer - C | |
| 210. |
A force of 100 N increases the length of a given wiere by 0.1 mm. Then the force required to increase its length by 0.25 mm isA. 50 NB. 150 NC. 250 ND. 500 N |
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Answer» Correct Answer - C `(F_(2))/(F_(1))=(l_(2))/(l_(1))=(0.25)/(0.10)=(5)/(2)` `F_(2)=(5)/(2) xx F_(1)` `=(5)/(2)xx100 = 250N` |
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| 211. |
The length of a metal wire is l when the tension is F and x l when the tension si y F. Then the natural length of the wire isA. `((x-y)l)/((x-1))`B. `((y-x)l)/((y-1))`C. `((x-y)l)/((x+1))`D. `((y-x)l)/((y+1))` |
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Answer» Correct Answer - B `L=(T_(2)l_(1)-T_(1)l_(2))/(T_(2)-T_(1))=(yFl-Fxl)/(yF-F)=((y-x)l)/(y-1)`. |
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| 212. |
If a shear force of 3000 N is applied on a cube of side 40 cm, then displacement of the top surface of the cube when bottom surface is fixed, is `" "(eta=5xx10^(10)N//m^(2))`A. 15 mmB. 150 mmC. `15xx10^(-8)mu mu m`D. `15 mu m` |
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Answer» Correct Answer - B `eta=(Fh)/(Ax) therefore x=(Fh)/(A eta)` `=(3000 xx 40 xx 10^(-2))/(40xx40xx10^(-4) xx 5 xx 10^(10))` `=(3)/(2) xx 10^(-7) =1.5 xx 10^(-7)m=150xx10^(-9)m` `=150 nm.` |
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| 213. |
Find out the elongation in block. If mass area of cross-section and young modulus of block are m, A and y respectively.A. `(Fl)/(AY)`B. `(Fl)/(2AY)`C. `(Fl)/(3AY)`D. cannot extend |
| Answer» Correct Answer - B | |
| 214. |
Two person pull a rope towards themselves. Each person exerts a force of 100 N on the rope. Find the Young modulus of the material of the rope if it extends in length by 1 cm. Original length of the rope=2 m and the area of cross section =cm^2.A. `10^(5)N//m^(2)`B. `10^(6)N//m^(2)`C. `10^(7)N//m^(2)`D. `10^(8)N//m^(2)` |
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Answer» Correct Answer - D `y=(FL)/(Al) =(100xx2)/(2xx10^(-4) xx 1xx10^(-2)) = 10^(8)N//m^(2)`. |
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| 215. |
A metal wire of coefficient of linear expansion and Young modulus are `1xx10^(-5)//""^(@)C` and `10^(11)N//m^(2)` respectively is tied between two points rigidly at a temperature `40^(@)C`. If the temperature is decreased to `20^(@)C` the force required to hold the wire in newton is ( the length of the wire is 40 cm and area of cross section is `1 cm^(2)`)A. 20 NB. 200 NC. 2000 ND. 1000 N |
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Answer» Correct Answer - C `F=yA prop Delta t` `=10^(11) xx 10^(-4) xx 10^(-5) xx (40 xx 20) =10^(2) xx 20` `=2000N`. |
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| 216. |
A solid sphere of radius `R` made of a material of bulk modulus `B` is surrounded by a liquid in a cylindrical container. `A` massless piston of area `A` (the area of container is also `A`) floats on the surface of the liquid. When a mass `M` is placed on the piston to compress the liquid , fractional change in radius of the sphere is `(Mg)/(alpha AB)`. Find the value of `alpha`. |
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Answer» Correct Answer - C Increase in pressure is `Deltap = (Mg)/A` Bulk modulus is ` B =Delta_(p)/((DeltaV//V))` `:.(DeltaV)/V = (Delta_(p))/B =( Mg)/(AB)` ….(i) Also, the volume of the sphere is `V = 4/3 piR^(3) rArr (Delta V)/V = (3 Delta R)/R` or `(Delta R)/R = 1/3. (DeltaV)/R`, Using Eq.(i) , we get ` (DeltaR)/R =( Mg)/(3 AB) rArr :. alpha = 3` |
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| 217. |
A piece of cork starts from rest at the bottom of a lake and floats up. Its velocity v is plotted against time t. Which of the following best represents the resulting curve? A. B. C. D. |
| Answer» Correct Answer - A | |
| 218. |
Consider a rod of steel having radius of 8 mm and the length of 2 m. If a force of 150 kN stretches it along its lengths , then calculated the stress, percentage strain in the rod if the elongation in length is 7.46 mm. |
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Answer» Radius of rod,` r=8 mm=8xx10^(-3)`m,length, L=2 m Applied force, F=150 kN=`15xx10^(4)N` Cross-section area of wire, `A=pir^(2)=pixx(8xx10^(-3))^(2)=201xx10^(-6)m^(2)` `DeltaL=7.46 mm=7.46xx10^(-3)m`, Percentage strain = ? Stress in rod `=(F)/(A)=(15xx10^(4))/(201xx10^(-6))` `=0.0746 xx 10^(10)Nm^(-2)` `=7.46xx10^(8)Nm^(-3)` Longitude strain `=(DeltaL)/(L)=(7.46xx10^(-3))/(2)=3.73xx10^(-3)` Percentage strain `=3.73xx10^(-3)xx100=0.37 %` |
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| 219. |
If the angle of shear is `30^(@)` for a cubical body and the change in length is 250 cm, then what must be the volume of this cubical body. |
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Answer» Given, angle of shear `=30^(@)` and change in length, `DeltaL=250 cm =2.5 m` `therefore` Shear strain, tan`phi=(DeltaL)/(L)implies"tan"30^(@)=(2.5)/(L)` `L=(2.5)/("tan"30^(@))=(2.5)/(0.577)=4.332` Volume, `V=L^(3)=81.309 m^(3)` |
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| 220. |
Identify the case when an elastic metal rod does not undergo elongationA. it is pulled with a constant acceleration on a smooth horizontal surfaceB. it is pulled with constant acceleration on a smooth horizontal surfaceC. it is allowed to fall freelyD. All of the above |
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Answer» Correct Answer - C `T =O` is free fall. |
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| 221. |
Vessel of `1xx10^(-3) m^(3)` volume contains an oil. If a pressure of `1.2xx10^(5) N//m^(2)` is applied on it , then volume decreases by `0.3xx10(-3) m^(3)`. The bulk modulus of oil isA. (a) `6xx10^(10) N//m^(2)`B. (b) `4xx10^(5) N//m^(2)`C. (c) `2xx10^(7) N//m^(2)`D. (d) `1xx10^(6) N//m^(2) ` |
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Answer» Correct Answer - B `B = -(Deltap)/(DeltaV//V)` `((1.2xx10^(5))(1xx10^(-3)))/(0.3xx10^-3)` `= 4xx10^(5) N//m^(2)` |
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| 222. |
The breaking force of wire is `10^(4)`N and radius is `1xx10^(-3)`m. If the radius is `2xx10^(-3)`m, then the breaking force will beA. `4xx10^(4)N`B. `40xx10^(4)N`C. `0.04xx10^(4)N`D. `0.4xx10^(4)N` |
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Answer» Correct Answer - A `(F_(2))/(F_(1))=((r_(2))/(r_(1)))^(2)=((2xx10^(-3))/(1xx10^(-3)))^(2)=4` `F_(2)=4F_(1)` `=4 xx 10^(4)N`. |
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| 223. |
A body weighs 160g in air 130 g in water and 136g in oil what is the sspecific gravity of oil? |
| Answer» Specific gravity of oil `=("loss of weight in oil")/("loss of weight in water")=(160-136)/(160-130)=(24)/(30)=(8)/(10)=0.8` | |
| 224. |
The radius of a soap bubble is r. the surface tension of soap solution is T, keeping temperature constant, the radius of the soap bubble is doubled the energy necessary for this will be-A. `24pir^(2)T`B. `8pir^(2)T`C. `12pir^(2)T`D. `16pir^(2)T` |
| Answer» Correct Answer - A | |
| 225. |
A weight is suspended from a long metal wire. If the wire suddenly breaks, its temperatureA. risesB. fallsC. remains unchangedD. attains a value 0 K |
| Answer» Correct Answer - A | |
| 226. |
The ring of radius 1 m is lying on the surface of liquid. It is lifted. It is lifted from the liquid surface by a force of 4 newtons in such a way that the liquid film in it remains intact. The surface tension of liquid will beA. `(1)/(2pi)N//m`B. `(1)/(pi)N//m`C. `(1)/(3pi)N//m`D. `(1)/(4pi)N//m` |
| Answer» Correct Answer - B | |
| 227. |
The length of needle foating on the surface of water is 1.5 cm the force in addition to its weight required to lift the needle from water surface will be (surface tension of water `=7.5N//cm`)A. 22.5 NB. 2.25 NC. 0.25 ND. 225 N |
| Answer» Correct Answer - A | |
| 228. |
The length of needle floating on water is 2.5 cm. Calculate thhe added force required to pull the needle out of water `(T=7.2xx10^(-2)N//m)` |
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Answer» The force of surface tension `F=Txx2l(because` Two free surface are there) `impliesF=7.2xx10^(-2)xx2xx2.5xx10^(-2)=3.6xx10^(-3)N` |
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| 229. |
If two glass plates have water between them and are separated by very small distance (see figure). It is very difficult to pull them apart. It is because the water in between forms cylindrical surface on the side that gives rise ot lower pressure in the water in comparison to atmosphere. If the radius of the cylindrical surface is `R` and surface tension of water is `T` then the pressure in water between the plates is lowr by: A. `(2T)/(R)`B. `(4T)/(R)`C. `(T)/(4R)`D. `(T)/(2R)` |
| Answer» Correct Answer - B | |
| 230. |
Statement-1: The stream of water emerging from a wate tap "necks down" as it falls. Statement-2: The volume flow rate at different levels is same.A. Statement-1, is true, Statement-2 is true, Statement-2 is correct explanation for statement-1B. Statement-1 is true, statement-2 is true, statement-2 is NOT a correct explantion for statement-1C. statement-1 is true, statement-2 is falseD. statement-1 is false statement-2 is true |
| Answer» Correct Answer - A | |
| 231. |
If it takes 5 minutes to fill a 15 litre bucket from a water tap diameter `(a)/(sqrt(pi))` cm then the raynolds number for the flow is (density of water `=10^(3)kg//m^(3)` and viscosity of water `=10^(-3)Pa`.s) close toA. 11000B. 5500C. 550D. 1100 |
| Answer» Correct Answer - B | |
| 232. |
A plate moves normally with the speed `v_(1)` towads a horizontal jet of uniform area of cross-section. The jet discharge water at the rate of volume `V` per second at a speed of `v_(2)`. The density of water is `rho`. Assume that water splashes along the surface of the plate ar right angles to the original motion. The magnitude of the force action on the plate due to the jet of water is |
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Answer» Correct Answer - D `F=(Deltap)/(Deltat)=(m(v_(1)+v_(2)))/(Deltat)=Vrho(V_(1)+V_(2))` where `(m)/(Deltat)=V="Volume"//sec` |
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| 233. |
A cylinder of height H and radius R is filled with a liquid of density p . What is the disrupting stress at a heght h? where is it maximum and where minimum ? [Hint : Disrupting stress is the elastic force per unit length Consider equilibrium of an element of the wall.] |
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Answer» Correct Answer - `pgR(H-h), F_(max)=pgRH,F_(min)=0` |
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| 234. |
A Copper wire and steel of the same diameter and length are connected end to end and a force is applied, which stretches their combined length by 1 cm. The two wires will haveA. Different stresses and strainsB. The same stress and strainC. The same strain but different stressesD. The same stress but different strains. |
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Answer» Correct Answer - D |
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| 235. |
Assertion Bulk modulus of elasticity of gases is pressure dependent. Reason More the pressure of gas, more is the Bulk modulus of elasticity of gas.A. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. If Assertion is true but Reason is false.D. If both Assertion and Reason are false. |
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Answer» Correct Answer - A (a) If pressure of gas is more, it is more difficult to compress a gas. Therefore, bulk modulus is high. |
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| 236. |
Assertion : If pressure is increased , bulk modulus of gases will increase. Reason : With increase in pressure , temperature of gases also increases .A. (a) If both Assertion and Reason are true and the Reason is correctn explanation of the Assertion.B. (b) If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.C. If Assertion is true, but the Reason is false.D. If Assertion is false but the Reason is true. |
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Answer» Correct Answer - C At highr pressure ,it is difficult to press the gas more. So, bulk modulus is high. |
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| 237. |
The elasticity of invarA. increases with temperature riseB. decrease with temperature riseC. does not depend on temperatureD. none of the above |
| Answer» Correct Answer - C | |
| 238. |
After effects of elasticity are maximum forA. glassB. quartzC. rubberD. metal |
| Answer» Correct Answer - A | |
| 239. |
The dimensionless quantity isA. stressB. shear stressC. strainD. restoring force |
| Answer» Correct Answer - C | |
| 240. |
Match the following columns. `{:(,"Column I",,"Column II"),((A),"Longitudinal stress",(p),"Volume changes"),((B),"Shear stress",(q),"Shape change"),((C),"Volumetric stress",(r),"Volume does not changes"),((D),"Tensile stress",(s),"Shapes does not change"):}`A. `{:(A,B,C,D),("p,s","q,r","p,s","p,s"):}`B. `{:(A,B,C,D),("q,r","p,s","p,s","p,s"):}`C. `{:(A,B,C,D),("p,s","p,s","q,r","p,s"):}`D. `{:(A,B,C,D),("p,s","p,s","p,s","q,r"):}` |
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Answer» Correct Answer - a (a) Volume changes in case of longitudinal and tensile stress whereas shape gets changed in shear stress. |
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| 241. |
One end of steel wire is fixed ti ceiling of an elevator moving up with an acceleration `2 m//s^(2)` amd a load of 10 kg hangs from other end. Area of cross- section of the wire is `2cm^(2)` .The longitudinal strain in the wire is `(g= 10 m//s^(2) and Y= 2 xx 10^(11)Nm^(2))`.A. ` 4 xx 10^(10)`B. `3 xx 10 ^(-6)`C. `8 xx 10 ^(-6)`D. ` 2 xx 10 ^(-6)` |
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Answer» Correct Answer - B (b) As, `T=m(g+a_(0))=10(10+2)=120N` Stress `=(T)/(A)=(120)/(2xx10^(4))=60xx10^(4)Nm^(-2)` and `Y=("Stress")/("Strain"), "Strain"=("Stress")/(Y)` `=(60xx10^(4))/(2xx10^(11))` `=30xx10^(-7)=3xx10^(-6)` |
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| 242. |
Two exactly similar wire of steel and copper are stretched by equal force. If the difference in their elongations is 0.5 cm, the elongation `(l)` of each wire is `Y_(s)("steel") =2.0xx10^(11) N//m^(2)` `Y_(c)("copper")=1.2xx10^(11)N//m^(2)`A. `l_(s)=0.75 cm,l_(c)=1.25 cm`B. `l_(s)=1.25 cm,l_(c)=0.75 cm`C. `l_(s)=0.25 cm,l_(c)=0.75 cm`D. `l_(s)=0.75cm,l_(c)=0.25 cm` |
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Answer» Correct Answer - A |
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| 243. |
In a wire, when elongation is 2cm, energy stored is E. If it is stretched by 10 cm, then the energy stored will beA. EB. 2 EC. 4 ED. 25 E |
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Answer» Correct Answer - D `(E_(2))/(E_(1))=((x_(2))/(x_(1)))^(2)=((10)/(2))^(2)=25` `E_(2)=25E_(1)`. |
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| 244. |
Which of the following is correct statement from the given graph plotted, for four wires of same material and same thickness A. A has largest lengthB. D has largest lengthC. C has least lengthD. B has largest length |
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Answer» Correct Answer - A `F=(yAl)/(L) prop (l)/(L)` For wire A has max length. |
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| 245. |
The length of a wire is increased by 1 mm due to applied load. The wire of the same material have lengths and radius half that of the first wire, by the application of the same force, then extension produced will beA. 2 mmB. 0.5 mmC. 4 mmD. 0.25 mm |
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Answer» Correct Answer - A `Y=(F)/(pi r^(2)) xx (L)/(l_(1))` `therefore l_(1)=(FL_(1))/(pi r_(1)^(2)y) and l_(2)=(FL_(2))/(pi r_(2)^(2)y)` `(l_(1))/(l_(2))=(L_(1))/(L_(2)) xx (r_(2)^(2))/(r_(1)^(2))` |
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| 246. |
For wires of the the same material are stretched by the same load. The dimensions are given below, which of them will elongate most ?A. length 100 cm, diameter 1 mmB. length 200 cm, diameter 2 mmC. length 300 cm, diameter 3 mmD. length 400 cm, diameter 0.5 mm |
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Answer» Correct Answer - D `Y=(F)/(pi r^(2//4)) xx (L)/(Delta l)=Delta prop (L)/(r^(2))` Hence `L//r^(2)` is maximum when `L=400` cm and D = 0.5 mm as compared to other cases. |
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| 247. |
The stress in a wire of diameter 2 mm, if a load of 100 g is applied to a wire, isA. `3.1xx10^(5)N//m^(2)`B. `6.2xx10^(5)N//m^(2)`C. `1.5xx10^(5)N//m^(2)`D. `12.4xx10^(5)N//m^(2)` |
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Answer» Correct Answer - A Stress `=(F)/(A) =(mg)/(pi r^(2))=(100 xx 10^(-3) xx 10)/(3.14 xx 10^(-6))` `=(1)/(3.14) xx 10^(6) =3.1 xx 10^(5)` |
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| 248. |
The load versus elongation graph for four wires of the same material is shown in the figure. The thickest wire is represented by A. ODB. OCC. OBD. OA |
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Answer» Correct Answer - A |
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| 249. |
The load versus elongation graph for four wires of the same material is shown in the figure. The thickest wire is represented by A. ODB. OCC. OBD. OA |
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Answer» Correct Answer - A (a) Elongation of the wire `Deltal=(FL)/(AY)` `therefore Deltal prop (1)/(r^(2))" "`(Y, L and F are constants) i.e., for the same load, thickest wire will show minimum elongation. So, line OD represent the thickest wire. |
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| 250. |
A copper rod 2m long is stretched by 1 mm, the energy stored per unit volume is, `(Y=1.2xx10^(11)N//m^(2))`A. `10xx10^(3)J//m^(3)`B. `20xx 10^(3)J//m^(3)`C. `5xx10^(3)J//m^(3)`D. `15xx10^(3)J//m^(3)` |
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Answer» Correct Answer - D `u=(1)/(2) " Stress" xx "Strain"=(1)/(2) Y("Strain")^(2)` |
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