Physics_NIS_Deformation

1.

Today’s
topic
• Deformation: Causes and Types
• Hookes law.Definition of load,extension, elastic limit and spring
constant.

2.

Today’s
Objectives
(a) appreciate that deformation is caused by a force and that, in one
dimension, the deformation can be tensile or compressive;
(b) distinguish between elastic and plastic deformation of a material;
(c) describe the behaviour of springs in terms of load, extension, elastic
limit, Hooke’s law and the spring constant (i.e. force per unit
extension);

3.

Science
Talk
How are these materials different?

4.

Science
Talk
What is deformation ?
How many types of deformation do you know ?
What is plastic deformation
What is elastic deformation ?
To distinguish between types of deformation ?

5.

KEY TERMS

6.

Deformation Forces
Types of deformation
https://www.youtube.com/watch?v=JT9b2VCzCe0

7.

Deformation Forces

8.

Forces Types
Forces don’t just change the motion of a body, but can change the size
and shape of them too. This is known as deformation.
Forces in opposite directions stretch or compress a body
When two forces stretch a body, they are described as tensile
When two forces compress a body, they are known as compressive

9.

10.

Extension and Compression
When you apply a
force (load) onto a
spring, it produces
a tensile force and
causes the spring
to extend
Stretching

11.

Tensile Strength
Tensile strength is the
amount of load or stress a
material can handle until it
stretches and
breaks

12.

Deformation Types
Small
FORCE
ELASTIC DEFORMATION
• Temporary shape change
• when the load is
removed, the object will
return to its original
shape
• Caused by smaller forces
Large
FORCE
PLASTIC DEFORMATION
• Permanent shape change
• when the load is
removed, the object will
not return to its original
shape or length. This is
beyond the elastic limit
• Caused by larger forces

13. Definitions

• Elastic Deformation
• when the deforming force is removed, the object will return to it’s original
shape
• eg rubber band, spring (usually)
• Plastic Deformation
• when the deforming force is removed, the object will not return to it’s original
shape
• eg Plasticine, Blutack

14. Elastic Properties of Matter

An elastic body is one that returns to its original shape after a
deformation.
Golf Ball
Rubber Band
Soccer Ball

15. Elastic Properties of Matter

An inelastic body is one that does not return to its original
shape after a deformation.
Dough or Bread
Clay
Inelastic Ball

16.

Deformation Types

17.

Deformation Types
Elastic Limit
Breaking Point
Proportionality Limit