Question related two different ways to do solution

  • Thread starter Thread starter helloword365
  • Start date Start date
AI Thread Summary
The discussion revolves around the different methods used to solve a problem involving cross-section sidelengths. One method expresses the sidelength as 8-8x/3, while the other relies on similar triangle relationships. The user questions the correctness of both approaches and seeks clarification on which answer is accurate, either 470 kJ or 117 kJ. There is also a suggestion to try the integral method indicated in red. The conversation highlights the complexities of solving the problem and the potential for multiple valid approaches.
helloword365
Messages
7
Reaction score
2
Homework Statement
An upside-down square pyramid with a height of 3 m and side lengths of 8m is filled to the brim with water. How much work is needed to lift all the water out of the container through the top. (ρ = 1000 kg/m3, g = 9.8 m/s2)
Relevant Equations
Work = Force * displacement
My work:
Screenshot 2025-04-12 203210.png


Answer Key (red font one) *may not be right.

My question is why is sidelength of cross section written as 8-8x/3, while my way of doing it doesn't involve that (involves suspicious similar triangle relationships)? Which answer (if any) is right here? 470 kj or 117 kj? Thank you!

Screenshot 2025-04-12 203210.png


Screenshot 2025-04-12 203309.png
 
Last edited by a moderator:
Physics news on Phys.org
Did you try doing the integral in red?
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Correct statement about a reservoir with an outlet pipe'
The answer to this question is statements (ii) and (iv) are correct. (i) This is FALSE because the speed of water in the tap is greater than speed at the water surface (ii) I don't even understand this statement. What does the "seal" part have to do with water flowing out? Won't the water still flow out through the tap until the tank is empty whether the reservoir is sealed or not? (iii) In my opinion, this statement would be correct. Increasing the gravitational potential energy of the...
Back
Top