Q.

The energy of a system is given as E(t)=α3e–βt, where t is the time and β=0.3 s–1. The error in the measurement of α and t are 1.2% and 1.6%, respectively. At t = 5 s, maximum percentage error in the energy is          [2025]

1 4%  
2 11.6%  
3 6%  
4 8.4%  

Ans.

(3)

dE=3α2dαe–βt+α3e–βt(–β)dt

dEE=3dαα+(–β)dt

△EE=3△αα+β△t

(%)△T=1.6×5=8%

%(3△αα)=3×1.2%=3.6%

Putting values we get,

△EE%=3.6+8×0.3=6%.