Question

Assertion (A) : Lead is more elastic than rubber.
Reason (R) : If the same load is attached to lead and rubber wires of the same cross-sectional area, the strain of lead is very much less than that of rubber.

• A. Both assertion and reason are true and the reason is correct explanation of the assertion
• B. Both assertion and reason are true, but reason is not correct explanation of the assertion
• C. Assertion is true, but the reason is false
• D. Assertion is false, but the reason is true

Answer 1

The correct option is A Both assertion and reason are true and the reason is correct explanation of the assertion

More elastic the material higher the Young's Modulus.
Young's Modulus of rubber is 0.01-0.1 Gpa whereas for Lead it is 16 Gpa.
Also, $Y=\left(F/A\right)/l/L$
F - Applied Force
A - Cross Section Area
l - Elongation/Decrease in Length
L - Actual Length
Therefore $l/L=F/AY$
for F,A same
$l/L$ is inversely proportional to $Y$
So, higher the Young's Modulus, lesser is the strain.