The temperature of a body falls from 40 ° C to 36 ° C in 4 minutes , when placed in a constant ambient temperature of 20 ° C . The time it takes for the temperature to fall from 36 ° C to 32 ° C in the same ambient temperature is

Question

The temperature of a body falls from 40 ° C to 36 ° C in 4 minutes , when placed in a constant ambient temperature of 20 ° C . The time it takes for the temperature to fall from 36 ° C to 32 ° C in the same ambient temperature is, 5 . 1 min, 6 . 8 min, 9 min, 7.2 min

MARKS App · Accepted Answer

Let θ be instantaneous temperature, θ For 40 ° C → 36 ° C 36 - 40 4 = - k ( 38 - 20 ) . . . ( i ) θ a v g = 38 ° C For 36 ° C → 32 ° C 32 - 36 t = - k ( 34 - 20 ) . . . ( ii ) θ a v g = 34 ° C ( i ) ( ii ) Gives t = 4 18 14 ⇒ t = 5 . 1 min

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