Deformation of solids

Question 1

What are tensile forces?

Answer 1

🔹When two forces stretch a body, they are known as tensile.

Question 2

What are compressive forces?

Answer 2

🔹When two forces compress a body, they are known as compressive.

Question 3

Tensile strength:

Answer 3

🔹 The amount of load or stress a material can handle until it stretches and breaks.

Question 4

The limit of proportionality:

Answer 4

🔹The point beyond which Hooke’s law is no longer true when stretching a material i.e the extension is no longer proportional to the applied load.

Question 5

How does Hooke’s law apply to compression?

Answer 5

🔹An applied force is now proportional to the decrease in length whereas in extension it’s the increase.

Question 6

Hooke’s Law :

Answer 6

🔹A material obeys Hooke’s Law if it’s extension is directly proportional to the applied force (load).

🔹F = k × x

Question 7

What is the spring constant? (K)

Answer 7

🔹It is defined as the force per extension up to the limit of proportionality.

🔹It is a measure of the stiffness of a spring.

🔹A stiffer spring will have a larger value of k.

🔹SI unit is N/m

🔹k = F/x

🔹Gradient of a force v extension graph

Question 8

Tensile Stress :

Answer 8

🔹It is the applied force per unit cross sectional area of a material.

🔹Unit is pascal.

Question 9

Strain :

Answer 9

🔹Strain is the extension per unit length

🔹No unit.

Question 10

Young’s Modulus :

Answer 10

🔹is the measure of the ability of a material to withstand changes in length with added load.

🔹This gives info about the elasticity of a material.

🔹defined as the ratio of stress and strain.

🔹Unit is pascal

Question 11

Elastic Deformation :

Answer 11

🔹When the load will is removed, the object will return to it’s original shape or length.

Question 12

Plastic deformation :

Answer 12

🔹When the load is removed, the object will not return to it’s original shape or length. This is beyond the elastic limit.

Question 13

Elastic Limit :

Answer 13

🔹The point beyond which the object does not return to it’s original length when the load is removed.

Question 14

What are brittle materials?

Answer 14

🔹Brittle materials have little to no plastic region.

🔹For eg: glass, concrete.

🔹The material breaks with little elasticity and insignificant plastic deformation.

Question 15

What are ductile materials?

Answer 15

🔹They have a larger plastic region

🔹For eg: rubber or copper.

🔹The materials stretches into a new shape before breaking.

Question 16

What is the area under a force extension graph?

Answer 16

🔹The work done in stretching a material is equal to the force multiplied by the distance moved.

🔹 Therefore, the area under a force-extension graph is equal to the work done to stretch the material.

🔹The work done is also equal to the elastic potential energy stored in the material.

Question 17

Elastic potential energy :

Answer 17

🔹It is defined as the energy stored within a material when it is stretched or compressed (when it obeys Hooke’s law)

🔹It can be found from the area under a force extension graph.