Define Elastic, Elasticity, Plasticity and Perfect Plastic Body | Class 11 Physics Chapter 8

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Learn the concepts of Elastic, Elasticity, Plasticity, Perfectly Elastic Body, and Perfect Plastic Body in Class 11 Physics Chapter 8. Includes definitions, examples, FAQs, MCQs, true-false questions, and short answer questions for NCERT, JEE, and NEET preparation in Physicshund

1. Elastic

A material is said to be elastic if it regains its original shape and size after the removal of the deforming force.

Example: Steel spring, quartz fibre.

2. Elasticity

Elasticity is the property of a material by virtue of which it regains its original shape and size completely when the deforming force is removed.

Ncert Definition 

Elasticity is the property of a body that enables it to regain its original configuration after the removal of the deforming force.

3. Perfectly Elastic Body

A body that completely regains its original shape and size after the removal of the deforming force is called a perfectly elastic body.

Example: No material is perfectly elastic in practice, but quartz fibre is considered nearly perfectly elastic.

4. Plastic

A material is said to be plastic if it does not regain its original shape and size after the removal of the deforming force.

Example: Clay, putty, wax.

5. Plasticity

Plasticity is the property of a material by virtue of which it undergoes permanent deformation and does not return to its original shape and size when the deforming force is removed.

Ncert Definition 

Plasticity is the tendency of a material to retain its deformed shape after the deforming force is removed.

6. Perfect Plastic Body

A body that retains the entire deformation produced in it even after the removal of the deforming force is called a perfect plastic body.

Example: Putty and wet clay are approximately perfect plastic bodies.

Frequently Asked Questions (FAQs)

Q1. What is elasticity?

Answer: Elasticity is the property of a material by which it regains its original shape and size after the deforming force is removed.

Q2. What is an elastic body?

Answer: An elastic body is one that returns to its original shape and size after the removal of the deforming force.

Q3. What is a perfectly elastic body?

Answer: A perfectly elastic body completely regains its original shape and size after deformation.

Q4. What is plasticity?

Answer: Plasticity is the property of a material to retain its deformed shape after the deforming force is removed.

Q5. Give examples of plastic materials.

Answer: Clay, wax, and putty are common examples of plastic materials.

Q6. Is any material perfectly elastic in nature?

Answer: No material is perfectly elastic in nature, though quartz fibre is nearly perfectly elastic.

Q7. What is a perfect plastic body?

Answer: A perfect plastic body retains the entire deformation even after the deforming force is removed.

True or False

  1. An elastic body regains its original shape after the deforming force is removed. (True)
  2. Plastic materials completely regain their original shape after deformation. (False)
  3. Elasticity is the property of retaining permanent deformation. (False)
  4. Clay is an example of a plastic material. (True)
  5. A perfectly elastic body regains its original dimensions completely. (True)
  6. Putty is approximately a perfect plastic body. (True)
  7. Plasticity and elasticity are the same properties. (False)
  8. Quartz fibre is nearly perfectly elastic. (True)
  9. Wax behaves as a plastic material. (True)
  10. All materials are perfectly elastic. (False)

Short Answer Questions

1. Define elasticity.

Elasticity is the property of a body by which it regains its original shape and size after the removal of the deforming force.

2. Define plasticity.

Plasticity is the property of a material to retain permanent deformation after the deforming force is removed.

3. What is an elastic body?

A body that regains its original shape and size after deformation is called an elastic body.

4. What is a plastic body?

A body that does not regain its original shape and size after deformation is called a plastic body.

5. Give one example each of elastic and plastic materials.

Elastic material: Steel spring; Plastic material: Clay.

6. What is a perfectly elastic body?

A body that completely regains its original shape and size after deformation.

7. What is a perfect plastic body?

A body that retains the entire deformation after the deforming force is removed.

MCQ Quiz

1. The property by which a body regains its original shape after deformation is called:

A) Plasticity
B) Elasticity
C) Rigidity
D) Viscosity

Answer: B) Elasticity

2. Which of the following is nearly a perfectly elastic material?

A) Clay
B) Wax
C) Quartz Fibre
D) Putty

Answer: C) Quartz Fibre

3. Which of the following is a plastic material?

A) Steel Spring
B) Quartz Fibre
C) Clay
D) Glass Fibre

Answer: C) Clay

4. Plasticity is the property of:

A) Recovering original shape completely
B) Retaining permanent deformation
C) Conducting heat
D) Reflecting light

Answer: B) Retaining permanent deformation

5. Putty is approximately a:

A) Perfectly Elastic Body
B) Perfect Plastic Body
C) Rigid Body
D) Brittle Body

Answer: B) Perfect Plastic Body

6. A perfectly elastic body:

A) Retains deformation permanently
B) Partially regains its shape
C) Completely regains its original shape and size
D) Breaks after deformation

Answer: C) Completely regains its original shape and size

7. Which property is opposite to plasticity?

A) Density
B) Elasticity
C) Pressure
D) Stress

Answer: B) Elasticity

Quick Revision

  • Elastic: Regains original shape and size after force is removed.
  • Elasticity: Property of regaining original shape and size.
  • Perfectly Elastic Body: Completely regains original shape and size after deformation.
  • Plastic: Does not regain original shape and size after force is removed.
  • Plasticity: Property of retaining permanent deformation.
  • Perfect Plastic Body: Retains the entire deformation after force is removed.

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