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Tuesday, November 13, 2018

Solution to JEE Mains 2018 Physics Q1


Q1. 1. The density of a material in the shape of a cube is determines by measuring three sides of
the cube and its mass. If the relative errors in measuring the mass and length are respectively
1.5% and 1%, the maximum error in determining the density is :
(1) 2.5%
(2) 3.5%
(3) 4.5%
(4) 6%

Ans-

Density(ρ)=Mass(M)Volume(V)
Here, the material is cube (dimension, L).
ρ=ML3 ρ=ML3
Maximum error in determining the density
Δρρ=ΔMM+3ΔLL
Δρρ=1.5+3×1
=4.5%
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Combination of Errors:
1) Error of a sum or difference >
D = A + B, then maximum error in D will be ΔD = ΔA + ΔB
2) Error of a product or quotient >
a) D = AB, then the relative error in D is:
(ΔD/D) = (ΔA/A) + (ΔB/B)
b) D=A3B2C3
The relative error in D is
(ΔD/D) = 3(ΔA/A) + 2(ΔB/B) + 3 (ΔC/C) (Note: errors are always additive in nature (physics))
Why-errors-are-always-additive-in-nature-physics
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Type in latex

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