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Mechanical Properties of Solids

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Physics Part II

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Physics

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CBSE Gujarat Board Haryana Board

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Class 10 Class 12
One meter long elastic wire is fixed at one end and at the other end a weight of 3kg is attached. The mass is pulled away from vertical line (passing through point of suspension) to a distance 0.6m and made to revolve with horizontal circle of radius 0-6m. Find the increase in length of the wire. Given that area of cross-section of wire 2x10–7m2 and Young's modulus of material of wire 2.5x1010 N/m2.

The given question is illustrated in the figure. below.




From right angled ΔSOA,

s i n theta equals fraction numerator 0.6 over denominator 1 end fraction equals 0.6
therefore space space space space space space c o s theta equals square root of 1 minus s i n squared straight theta end root equals 0.8

The different forces acting on mass are:

(i) Weight mg in vertically downward direction.

(ii) Tension T in the string along AS.

Now resolving the components of T as shown in fig. above.

The component Tcosθ balances the weight mg of the mass and component Tsinθ provides the necessary centripetal force to whirl the mass.

straight i. straight e. space space space space space space space straight T space c o s theta equals m g space space space space space space space space space space space space space space space space space space.... left parenthesis 1 right parenthesis

rightwards double arrow space space space space space space straight T equals fraction numerator m g over denominator c o s theta end fraction equals fraction numerator 3 cross times 9.8 over denominator 0.8 end fraction equals 36.75 straight N
N o w comma
space space space space space space space space space space space straight Y equals fraction numerator straight T divided by straight A over denominator capital delta l divided by straight l end fraction

rightwards double arrow space space space space space capital delta l equals fraction numerator Y l over denominator Y A end fraction
space space space space space space space space space space space space space equals fraction numerator 36.75 cross times 1 over denominator 2.5 cross times 10 to the power of 10 cross times 2 cross times 10 to the power of negative 7 end exponent end fraction

space space space space space space space space space space space space space equals 7.35 cross times 10 to the power of negative 3 end exponent straight m equals 7.35 m m

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What is the nature of inter-atomic or inter-molecular forces?

Inter-atomic or inter-molecular forces are electrostatic in nature. 

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What is the force of cohesion?

Cohesive attraction or cohesive force is the force of attraction between same types of molecules sticking together. 
651 Views

What do you understand by intermolecular forces?

Intermolecular force is the force between the molecules of the substance is called intermolecular force.

There is a dipole-dipole interaction between the molecules.
630 Views

Define interatomic forces and give an example?

The force between atoms of the molecule is called interatomic force.

E.g.The nucleus and electron cloud of a molecule is binded by electrostatic force. 
1032 Views

What is the force of adhesion?

Adhesive force is the attractive force between two unlike molecules. They are caused by forces acting between two substances like electrostatic force (attraction due to opposing charges), mechanical force etc. 

E.g., Force of attraction between gum and paper.

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