FOLLOW US ON TWITTER
SHARE THIS PAGE ON FACEBOOK, TWITTER, WHATSAPP ... USING THE BUTTONS ON THE LEFT


YOUR PARTICIPATION FOR THE GROWTH OF PHYSICS REFERENCE BLOG

Thursday, January 16, 2020

A steel string on an electric guitar has the following properties.


Question 14
A steel string on an electric guitar has the following properties.

diameter = 5.0 × 10-4 m
Young modulus = 2.0 × 1011 Pa
tension = 20 N

The string snaps, and contracts elastically.

By what percentage does a length l of a piece of the string contract?
A 5.1×10-4 %             B 5.1×10-2 %             C 1.3×10-4 %                         D 1.3×10-2 %





Reference: Past Exam Paper – November 2009 Paper 11 Q22 & Paper 12 Q21





Solution:
Answer: B.


Percentage of the length that contracts = e/L × 100%

But e/L is the strain of the string.
So, percentage of the length that contracts = strain × 100%


Young modulus, E = stress / strain
Strain = Stress / E
Stress = F / A
Strain = F / EA

Cross-sectional area. A = πd2 / 4

Strain = 20 / [(2.0×1011) × (Ï€×(5.0×10-4)2/4)]

Strain × 100% = {20 / [(2.0×1011) × (Ï€×(5.0×10-4)2/4)]} × 100%
Strain × 100% = 0.0509 % = 5.1×10-2 %

No comments:

Post a Comment

If it's a past exam question, do not include links to the paper. Only the reference.
Comments will only be published after moderation

Currently Viewing: Physics Reference | A steel string on an electric guitar has the following properties.