# 11 - Elasticity Questions Answers

Joshi sir comment

Due to inner sphere attraction, outer sphere contracts so it is compressive stress.

Physics >> Mechanics Part 2 >> Elasticity Medical Exam

A solid sphere is subjected to uniform pressure from all direction. The ratio of volumetric strain to lateral strain produced in it, is

Joshi sir comment

V = 4/3 πr3

so dV = 4πr2

now calculate dV/V

Physics >> Mechanics Part 2 >> Elasticity Medical Exam

What is the length of a wire whose density is 8 g/cm3, which suspended vertically, would break due to its own weight? [Breaking stress of wire is 2.4 x 108 N/m2]

Joshi sir comment

use stress = force/area

Physics >> Mechanics Part 2 >> Elasticity Medical Exam

When a load of 8 kg is hung on a wire, then extension of 3 cm takes place, the work done by internal forces of wire is

Joshi sir comment
Calculate work done by weight of body hung
Physics >> Mechanics Part 2 >> Elasticity Medical Exam

The work done per unit volume to stretch the length of area of cross-section 2 mm2 by 2% will be [ Y = 8 x 1010 N/m2 ]

Joshi sir comment
W =1/2 Y (dl/l)2 V V represents volume Now solve
Physics >> Mechanics Part 2 >> Elasticity Medical Exam

To break a wire a stress of 9 x 105 N/m2 is required. If density of the material of wire is 3 g/cc, then the minimum length of wire which will break by its own weight will be

Joshi sir comment

use stress = force /area

Physics >> Mechanics Part 2 >> Elasticity Medical Exam

A steel wire is 1m long and 1mm2 in area of cross-section. If it takes 200 N to stretch this wire by 1mm, how much force will be required to stretch a wire of the same material as well as diameter from its normal length of 10m to a length of 1002 cm?

Joshi sir comment

by first set of data calculate Y then by using this Y solve the question

Physics >> Mechanics Part 2 >> Elasticity Medical Exam

The length of wire, when M1 is hung from it, is l1 and is l2 with both M1 and M2 hanging. The natural length of wire is [ M2 is on M1 ]

Joshi sir comment

Y = M1gL/A(l1-L) = (M1+M2)gL/(l2-L)

solve for L

Physics >> Mechanics Part 2 >> Elasticity Medical Exam

A nylon rope 3 cm in diameter has a breaking strength of 1.5 x 105 N. The breaking strength for a similar rope 1.5cm in diameter is