# Mechanical Properties Of Solids (Physics 11th class Amazing Concept)

Mechanical Properties Of Solids best and easy definition is here. If you want to know Mechanical Properties Of Solids hidden concept. Then enjoy your expectation. Because i am explaining here, Mechanical properties of solid very simple, with easy tips.

So you can remember concept easily and never forget. And full enjoy learning Mechanical properties of solid ever before. Therefore lets start. What is in mechanical properties of solids ?

## What are the mechanical properties of solids ?

Well see the above pictures. These are some amazing building, bridges and crane. And many more you see everyday. So there all are solids. Which is made by solid substances. Hence in this post you are going to learn that things,

which need to know you for designing these solids.  Therefore you can think that, Whatever you are going to learn here, is very much physical and practical importance.

So this is very useful topic for engineering point of view. Hence all civil engineers must have depth knowledge of this topic.  Because civil engineers are responsible for designing this building and bridges.

So very first it is important to know. What is a Rigid body ? Well it is that body, which can’t be deform. In other words rigid body shape and size can’t change.  But if we talk practically. Then there is no any such type of body exist in the world, which is rigid. Hence every object shape and size can be change.

### Real example for mechanical solid compression and deformation

Now take some example for clarity. Suppose you have three metal, and these are rubber, spring and iron rod. If you are pulling with some forces at both end of rubber and spring. Then what is going to happen with rubber and spring.

So Obviously both rubber and spring shape will change. Now take iron rod and do the same. Then Can you tell me, what is happening in this case ? Well feel iron rod shape is not change.

But actually iron rod shape is change, very very small elongation, which is not visible to you. Therefore iron rod length is change in the same way, as rubber and spring length is change. But the only difference is iron rod elongation is very very small.

Similarly if any other metal rod like, Aluminium, copper glass, and you will pull at the both end with some forces, it is changed.  So in this topic, you are learning about the elongation, which is happening after stretch in depth.

Hence the first question arises that, why this elongation is done ?  Therefore to understand this chemistry concept. You can just think, rubber band is made with many molecules. Now what is molecules ? .

well it is smallest particle of a compound. Again this molecules are internally connected with small spring. And this is true for all the metal.  But the difference is only that, in case of rubber band.

These internal small spring between two molecules are lose.  And in case of iron rod that spring are tight spring. So iron rod elongation is very very small.

#### What are the elastic properties of solids ?

As seen from the above picture. Solids are made of molecules, and these molecules are connected with small spring in every objects. which are shown in picture.  Hence due to this properties solids are elastic in nature. Now let me ask a very simple question. So refer picture below.

Think and tell me, what is your answer ? Well in both the cases elongation will be same. But how and why ? See the difference in B case. And that is one end is fixed with wall. So think whenever you are pulling the other end, then rod will try to move ahead.

Hence the rod is pulling the wall ahead. Therefore according to Newton’s third law, Wall is pulling the rod with 100N force towards itself.  So effectively in both the cases, force is same. Hence the elongation is same in both the cases.

You are not seeing this force, but actually wall is pulling that end with 100N force towards itself. Now i am going to define some terms.  Which is very important, So you must know and remember that terms to understand this topic. So refer below picture.

##### What is stress and strain ?

Strain > is a unit less quantity. Because it is the ratio of length. It is also called longitudinal strain. There are three types of strain.  Which is given below.

• Longitudinal strain
• Shear strain
• Volume strain

Stress > it is define as restoring force/area = Stress = F/A and its unit is N/m*m or pascal. Here force F is restoring force, Not external force.  Which are called tensile and compressive stress.

Tensile stress is that stress in which length of the rod is increase. Whereas compressive stress is opposite of tensile. Hence in this case force direction is opposite and compressive in nature. Three are three types of Stress.

• Tensile Stress
• Shear Stress
• Volume Stress

##### Mechanical properties of solids class 11

Hook’s Law state about elasticity and plasticity of material. Now what is elasticity ? Well if you pull any object and released, and after release. if that object regain its original shape, then this is called elasticity.

So if any object which does’t gain its original shape, after pulling and release are called plastic material. Therefore Hook’s law also state that, Stress is directly proportional to strain, Within the elastic limit.

So which is more elastic rubber or steel ?  What is your answer. If your answer is rubber. Then your are wrong. Because steel is more elastic than rubber.  But how try to understand the point.

You feel that rubber regain its original shape, after removal of deforming force. Whereas steel does’t , So rubber is more elastic than steel. Of course you are right, but you must remember within the elastic limit.

Therefore within the elastic limit steel is more elastic than rubber. Because within elastic limit steel regain its shape faster than rubber. So steel is more elastic than rubber. I hope you got the point.

Inter molecular forces between two molecules, This is also called restoring force. Which is responsible for elasticity for any object. Refer above picture, small spring force in the picture.

###### What is elastic Behavior of solids  ?

Now you can ask, why is elasticity properties exist in any object ? As i told you inter molecular or restoring force is responsible for elasticity. So actually molecules of any object, want to live at a optimal distance.

This is called intramolecular distance, which is at minimum potential energy level. Because object is stable at minimum potential energy level.

Therefore as you apply deforming force on the object, Then molecules does’t want to displace from its intramolecular position, And apply a restoring force opposite to external deforming force.

Now you can solve numerical example with, help of formula derived for Stress, strain and Young’s modulus.

So if you want to learn more physics post. Then refer my previous post. This link is given below.

## 2 Replies to “Mechanical Properties Of Solids (Physics 11th class Amazing Concept)”

1. Ernesto Brancanto says:

Learned a whole lot. Quite simple to understand. Nice one for blogging 🙂