A cup of tea cools from 80 ° C to 60 ° C in 40 seconds . The ambient temperature is 30 ° C . In cooling from 60 ° C to 50 ° C , It will take time :

Question

A cup of tea cools from 80 ° C to 60 ° C in 40 seconds . The ambient temperature is 30 ° C . In cooling from 60 ° C to 50 ° C , It will take time :, 35 s, 30 s, 32 s, 48 s

MARKS App · Accepted Answer

From θ 2 - θ 1 t = k θ 1 + θ 2 2 - θ 0 we have 8 0 ∘ - 6 0 ∘ 4 0 ∘ = k 8 0 ∘ + 6 0 ∘ 2 - 3 0 ∘ ⇒ k = 1 8 0 Now 6 0 ∘ - 5 0 ∘ t = k 6 0 ∘ + 5 0 ∘ 2 - 3 0 ∘ ⇒ 1 0 t = 1 8 0 2 5 ⇒ t = 3 2 s

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