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### Course: Class 11 Physics (India)>Unit 13

Lesson 1: Stress, strain, and modulus of elasticity

# Solved example: Stress and strain

In this video, we will solve a numerical on calculating strain.  Created by Mahesh Shenoy.

## Want to join the conversation?

• I'm a little confused with the conversion of mm^2 to m^2. Don't you need to multiply the 5 by 10^-3 before you can use it to divide the 2000? Why is the 5 excluded from the parenthesis?
• I thought K (young's modulus) was only high when the material was highly elastic? So if according to the teacher, steel is very elastic with a high modulus, then why is the extension very small?
(1 vote)
• If the Nm^-2 cancels out on both sides of the equation, how come you still squared the number (5x10^-3) to get (5x10^-6)? and didn't square anything on the other side of the equation?
(1 vote)
• At why did he write the force = 2000N? If we multiply the mass of 200kg with the gravitational constant 9.8 m/s^2, the result comes to 1960 N.
(1 vote)
• g was approximated to 10 ms^-2
(1 vote)
• Why did you set delta L/L x 100 = our answer?
I don't understand why DeltaL/L comes from... Agh.
• Hooke's law tells us that ,for an object
stress=k*strain( under elastic limits)
Now, only for springs,
hooke's law=>Restoring force=-kx
For all other objects undergoing tensile or compressive strain, hook's law states that
Restoring force/area=k*strain

hope this helps.