Topic 5: Young’s Modulus

Young’s Modulus

Young’s modulus is a measure of the elasticity of a solid material. It indicates how much a material stretches or compresses when a force is applied along its length.

Definition

Young’s modulus is defined as the ratio of longitudinal stress to longitudinal strain within the elastic limit.

Formula for Young’s Modulus

Young’s Modulus (Y) = Longitudinal Stress / Longitudinal Strain

Since,
Stress = Force / Area
Strain = Change in length / Original length

Y = (F / A) / (ΔL / L)

Y = (F × L) / (A × ΔL)

SI Unit of Young’s Modulus

The SI unit of Young’s modulus is pascal (Pa).

Nature of Young’s Modulus

It is a measure of stiffness of a material
Higher value → material is more rigid
Lower value → material is more elastic

Examples

Steel has high Young’s modulus
Rubber has low Young’s modulus

Q1. Young’s modulus is the ratio of:
A) Stress to force
B) Strain to stress
C) Stress to strain
D) Force to area

Answer: C


Q2. SI unit of Young’s modulus is:
A) Newton
B) Joule
C) Pascal
D) Watt

Answer: C


Q3. Formula for Young’s modulus is:
A) Y = F / A
B) Y = ΔL / L
C) Y = (F × L) / (A × ΔL)
D) Y = m g h

Answer: C


Q4. A material having high Young’s modulus is:
A) Easily stretchable
B) Very elastic
C) Very rigid
D) Very soft

Answer: C


Q5. Young’s modulus is applicable for:
A) Volumetric stress
B) Shearing stress
C) Longitudinal stress
D) Thermal stress

Answer: C


Q6. A wire stretches more for the same force if its Young’s modulus is:
A) Large
B) Small
C) Infinite
D) Zero

Answer: B


Q7. Young’s modulus depends on:
A) Shape of material
B) Length of wire
C) Material of the wire
D) Applied force only

Answer: C


Q8. Which material has maximum Young’s modulus?
A) Rubber
B) Plastic
C) Steel
D) Wood

Answer: C

Chapter 6: Mechanical Properties of Solids