Answer :
The energy in an 871 KJ cup of yogurt will last for 18.71 minutes .
In the question ,
it is given that ,
efficiency is = 20% = 0.20 .
the rate of work is 155W ,
we know that Efficiency = [tex]\frac{E_{obtain} }{E_{consumed} }[/tex]
substituting the values ,
we get ,
[tex]E_{consumed}[/tex] = 155/0.20
= 775 J/sec .
This means that for work of 155W it require to consume energy at the rate of 775 J/sec .
we know that the formula for time , energy and rate is
Time = Energy/Rate
time = 871000/775
= 1123 seconds
= 18.71 minutes
Therefore , The energy in the yogurt will last for 18.71 minutes .
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