Physics Help Forum Require same or more WORK to pump from a (6" into a 3") than of a (6" into a 6"pipe)?

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 Aug 27th 2019, 03:28 PM #1 Junior Member   Join Date: Aug 2019 Posts: 2 Require same or more WORK to pump from a (6" into a 3") than of a (6" into a 6"pipe)? Instead of pumping from a 6" cylinder up into a 6" cylinder well i'm now pumping from a 6" cylinder up into a 3" diameter cylinder well. I'm unsure if this would require the same or more work to pump than if the entire well was just a (6"diameter well) due to the added friction. Nor do i even know where to begin on how to calculate the math of the added friction. Below is a labeled drawing of a hand pump and well. To avoid confusion both wells i speak of in the titled question do have the same amount of water in each as the only difference here is the changes of pipe dimension. DRAWING: The total amount of water in this well that's being lifted weighs 73.6 (lb). The work being done on the lever is: (Pump rod/Piston/73.6lb) (A) .. 2 ft to Pump's ^(FULCRUM)^ (B).. to 16ft Lever with a 10 (lb) load at the end (C). On a seesaw these loads would be at least equilibrium. WELL: 20ft height 3" diameter cylinder labeled (W). PUMP: 1ft height 6" diameter cylinder pump labeled (P). Total amount being pumped per stroke is (1.5 gallons) or 12.26 (lb) Attached Thumbnails   Last edited by Rip; Aug 29th 2019 at 12:18 PM. Reason: added photo
 Aug 29th 2019, 12:18 PM #2 Junior Member   Join Date: Aug 2019 Posts: 2 I'v added a photo. Thank you!
 Aug 29th 2019, 12:53 PM #3 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,354 Ignoring friction, the work per stroke of the pump is the same in both cases. Switching from to a 3" pipe from 6" means that with each stroke water is lifted 4 times as far in the pipe, but the weight of that water is 1/4 as great. Since work is calculated as force times distance, the calculation is the same in both cases. however, you are on the right track regarding friction. The greater water velocity in the 3" pipe and the smaller diameter means there is more resistance to water flow. Therefore it is more efficient to use a larger diameter pipe if possible. neila9876 likes this.
 Aug 30th 2019, 05:01 AM #4 Senior Member     Join Date: Jun 2016 Location: England Posts: 1,091 Hard Work Apart from the scientific work (in joules) there is also the common usage of work as in "how difficult is it" In scientific usage the total work is given by the rate of application of the work (joules per second) multiplied by the duration of the application of the work (seconds). So the same number of joules can be expended by expending little effort but over a huge time, or by expending a huge effort over a little time, or by expending a moderate effort over a moderate time. As a human our feeling of difficulty is non-linear with respect to both the rate of work and the duration. I suspect that, in most circumstances, we would feel that the sweet spot falls somewhere in the moderate region. __________________ ~\o/~

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