Question

Coefficient of linear expansion of brass and steel rods are $${\alpha _1}$$ and $${\alpha _2}.$$ Lengths of brass and steel rods are $${l_1}$$ and $${l_2}$$ respectively. If $$\left( {{l_2} - {l_1}} \right)$$  is maintained same at all temperatures, which one of the following relations holds good ?

A. $${\alpha _1}l_2^2 = {\alpha _2}l_1^2$$
B. $$\alpha _{_1}^2{l_2} = \alpha _2^2{l_1}$$
C. $${\alpha _1}{l_1} = {\alpha _2}{l_2}$$  
D. $${\alpha _1}{l_2} = {\alpha _2}{l_1}$$
Answer :   $${\alpha _1}{l_1} = {\alpha _2}{l_2}$$
Solution :
According to question,
Coefficient of linear expression of brass = $${\alpha _1}$$
Coefficient of linear expression of steel = $${\alpha _2}$$
Length of brass and steel rods are $${l_1}$$ and $${l_2}$$ respectively.
As given difference increase in length $$\left( {{{l'}_2} - {{l'}_1}} \right)$$  is same for all temperature.
So, $${{l'}_2} - {{l'}_1} = {l_2} - {l_1}$$
$$\eqalign{ & \Rightarrow {l_2}\left( {1 + {\alpha _2}\Delta t} \right) - {l_1}\left( {1 + {\alpha _1}\Delta t} \right) = {l_2} - {l_1} \cr & \Rightarrow {l_2}{\alpha _2} = {l_1}{\alpha _1} \cr} $$

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Basic Physics >> Mechanical Properties of Solids and Fluids

Releted Question 1

The following four wires are made of the same material. Which of these will have the largest extension when the same tension is applied?

A. $$length=50\,cm, \,\,diameter=0.5 \,mm$$
B. $$length = 100 \,cm, \,\,diameter= 1 \,mm$$
C. $$length= 200 \,cm, \,\,diameter= 2 \,mm$$
D. $$length=300 \,cm, \,\,diameter =3 \,mm$$
Releted Question 2

A U-tube of uniform cross section (see figure) is partially filled with a liquid I. Another liquid II which does not mix with liquid I is poured into one side. It is found that the liquid levels of the two sides of the tube are the same, while the level of liquid I has risen by $$2 \,cm.$$  If the specific gravity of liquid I is $$1.1,$$  the specific gravity of liquid II must be-
Mechanical Properties of Solids and Fluids mcq question image

A. $$1.12$$
B. $$1.1$$
C. $$1.05$$
D. $$1.0$$
Releted Question 3

A homogeneous solid cylinder of length $$L\left( {L < \frac{H}{2}} \right),$$   cross-sectional area $$\frac{A}{5}$$ is immersed such that it floats with its axis vertical at the liquid-liquid interface with length $$\frac{L}{4}$$ in the denser liquid as shown in the figure. The lower density liquid is open to atmosphere having pressure $${P_0}.$$ Then density $$D$$ of solid is given by-
Mechanical Properties of Solids and Fluids mcq question image

A. $$\frac{5}{4}d$$
B. $$\frac{4}{5}d$$
C. $$4d$$
D. $$\frac{d}{5}$$
Releted Question 4

A large open tank has two holes in the wall. One is a square hole of side $$L$$ at a depth $$y$$ from the top and the other is a circular hole of radius $$R$$ at a depth $$4y$$  from the top. When the tank is completely filled with water, the quantities of water flowing out per second from both holes are the same. Then, $$R$$ is equal to-

A. $$\frac{L}{{\sqrt {2\pi } }}$$
B. $$2\pi L$$
C. $$L$$
D. $$\frac{L}{{2\pi }}$$

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