Thermodynamics -- Calculations for heating water up

[tollf]

Homework Statement

nvm

Relevant Equations

nvm

A thermal flask with water of temperature 90c is placed out in room temperature 20c, sealed. How long before it reaches 55c?

outer radius and height: 5cm, 25cm

volume of water is 1litre.

R = 0.5 Km2/W

using this equation to solve it combining these two and integrating with respect to T.

ending up with this function. T0 for the original temp inside flask, and putting 55 for Th
Using a= 942.5, c = 4190, and m = 1. Not sure how I am suppose to use this because every answer i get seems weird

The actual formula is for calculating time for water to heat up to its surroundings so I am guessing i need to shuffle the values

 

[Chestermiller]

This is done pretty incorrectly. What value is TH supposed to be? What is the differential equation that you should be solving? What is the initial condition? What is the final temperature?

 

[berkeman]

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