Question

A small metal bar, whose initial temperature was 30° C, is dropped into a large container of boiling water. How long will it take the bar to reach 80° C if it is known that its temperature increases 2° during the first second? (The boiling temperature for water is 100° C. Round your answer to one decimal place.)

Answer 1

Answer:

t = 25s

Explanation:

The required temperature change is 50°C. (80 –30). The temperature of the bar increased 2°C in the first second. Assuming uniformity in the properties of the bar, in 2s the temperature would now be 2+2 = 4°C, in 3s it will be 2+2+2 =6°C.

So for gain a temperature change of 50°C, it will take 50/2 = 25s

ΔT /t = 2

t = ΔT/2 = 50/2 = 25seconds

Answer 2

Answer: It will take 43.2 seconds for the bar to reach 80 °C

Explanation: Please see the attachments below