Temperature and Internal Energy/Time to heat water

juanita
Messages
1
Reaction score
0
A cup of water is scooped up from a swimming pool of water. Compare the temperature T and the internal energy U of the water, in both the cup and the swimming pool.
a) Tpool is less than Tcup, and the U is the same.
b) Tpool is equal to Tcup, and Upool is less than Ucup.
c) Tpool is equal to Tcup, and Upool is greater than Ucup.
d) Tpool is greater than Tcup, and the U is the same.

A 5 kW heater is used to heat water. How long will it take to heat 20 kg of water from 20 degrees celsius to 100 degrees celsius?
a) 32 minutes
b) 2 minutes
c) 12 minutes
d) 22 minutes

any help would be appreciated, thanks!
 
Physics news on Phys.org
Welcome to PF :smile:

What are your thoughts on how to solve the problems? What equations (from your textbook or class lecture) do you think would apply here?
 
Hi, I had an exam and I completely messed up a problem. Especially one part which was necessary for the rest of the problem. Basically, I have a wormhole metric: $$(ds)^2 = -(dt)^2 + (dr)^2 + (r^2 + b^2)( (d\theta)^2 + sin^2 \theta (d\phi)^2 )$$ Where ##b=1## with an orbit only in the equatorial plane. We also know from the question that the orbit must satisfy this relationship: $$\varepsilon = \frac{1}{2} (\frac{dr}{d\tau})^2 + V_{eff}(r)$$ Ultimately, I was tasked to find the initial...
The value of H equals ## 10^{3}## in natural units, According to : https://en.wikipedia.org/wiki/Natural_units, ## t \sim 10^{-21} sec = 10^{21} Hz ##, and since ## \text{GeV} \sim 10^{24} \text{Hz } ##, ## GeV \sim 10^{24} \times 10^{-21} = 10^3 ## in natural units. So is this conversion correct? Also in the above formula, can I convert H to that natural units , since it’s a constant, while keeping k in Hz ?
Back
Top