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The New Coffee Room

  1. TNCR
  2. General Discussion
  3. Puzzle Time - Rolling Balls

Puzzle Time - Rolling Balls

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  • taiwan_girlT Offline
    taiwan_girlT Offline
    taiwan_girl
    wrote on last edited by
    #1

    Four identical ball on four different tracks are released at the same time. Which of the tracks - bent, straight, circular, or cycloidal - will deliver the ball to the end of the slope the fastest?

    IMG_4478 copy.jpg

    1 Reply Last reply
    • KlausK Online
      KlausK Online
      Klaus
      wrote on last edited by Klaus
      #2

      Interesting. I remember very little physics. But the total energy of the balls must stay the same. The initial energy is something like m* g * h if I remember correctly. This gets translated into a mix of rotational energy (how fast the ball rotates) and translational energy (how fast the ball moves). So I'd say the fastest ball is the one that rotates the slowest. I presume that the shortest track - the straight line - yields the slowest rotation, hence I'd go with that one.

      My confidence: About 40%.

      We are supposed to ignore heat, rolling resistance etc., right?

      KlausK 1 Reply Last reply
      • AxtremusA Offline
        AxtremusA Offline
        Axtremus
        wrote on last edited by
        #3

        ||Cycloidal, because that allows the fastest acceleration in the early phase of the roll.||

        1 Reply Last reply
        • A Offline
          A Offline
          AndyD
          wrote on last edited by
          #4

          Cycloidal (guessing the initial gravity/greater acc) Are they in order, right to left?

          1 Reply Last reply
          • L Offline
            L Offline
            Loki
            wrote on last edited by
            #5

            Wrong.

            ||we can’t we enough of the graph to know||

            1 Reply Last reply
            • jon-nycJ Offline
              jon-nycJ Offline
              jon-nyc
              wrote on last edited by
              #6

              ||Cycloidal. I know enough physics to work out a proof but the fact that high end skate pipes are cycloids tells me someone else already did.||

              You were warned.

              Aqua LetiferA 1 Reply Last reply
              • KlausK Klaus

                Interesting. I remember very little physics. But the total energy of the balls must stay the same. The initial energy is something like m* g * h if I remember correctly. This gets translated into a mix of rotational energy (how fast the ball rotates) and translational energy (how fast the ball moves). So I'd say the fastest ball is the one that rotates the slowest. I presume that the shortest track - the straight line - yields the slowest rotation, hence I'd go with that one.

                My confidence: About 40%.

                We are supposed to ignore heat, rolling resistance etc., right?

                KlausK Online
                KlausK Online
                Klaus
                wrote on last edited by
                #7

                @Klaus said in Puzzle Time - Rolling Balls:

                Interesting. I remember very little physics. But the total energy of the balls must stay the same. The initial energy is something like m* g * h if I remember correctly. This gets translated into a mix of rotational energy (how fast the ball rotates) and translational energy (how fast the ball moves). So I'd say the fastest ball is the one that rotates the slowest. I presume that the shortest track - the straight line - yields the slowest rotation, hence I'd go with that one.

                My confidence: About 40%.

                We are supposed to ignore heat, rolling resistance etc., right?

                Oh, I just see that I misread the question.

                You are asking for which ball reaches the end of the slope the fastest. I believe Jon is right about that one. Isn't that a famous historical problem?

                I somehow read your post as asking for which track yields the highest terminal speed, and I still guess that the straight line has that property.

                1 Reply Last reply
                • jon-nycJ jon-nyc

                  ||Cycloidal. I know enough physics to work out a proof but the fact that high end skate pipes are cycloids tells me someone else already did.||

                  Aqua LetiferA Offline
                  Aqua LetiferA Offline
                  Aqua Letifer
                  wrote on last edited by
                  #8

                  @jon-nyc said in Puzzle Time - Rolling Balls:

                  ||Cycloidal. I know enough physics to work out a proof but the fact that high end skate pipes are cycloids tells me someone else already did.||

                  ||Same. Acceleration's relationship to movement vectors and time is a thing.||

                  Please love yourself.

                  1 Reply Last reply
                  • HoraceH Offline
                    HoraceH Offline
                    Horace
                    wrote on last edited by
                    #9

                    This question is what defines a cycloid.

                    Education is extremely important.

                    KlausK 1 Reply Last reply
                    • HoraceH Horace

                      This question is what defines a cycloid.

                      KlausK Online
                      KlausK Online
                      Klaus
                      wrote on last edited by
                      #10

                      @Horace said in Puzzle Time - Rolling Balls:

                      This question is what defines a cycloid.

                      It is defined as the path shape which yields the fastest traveling time for a rolling ball.

                      1 Reply Last reply
                      • taiwan_girlT Offline
                        taiwan_girlT Offline
                        taiwan_girl
                        wrote on last edited by
                        #11

                        @AndyD @Axtremus @jon-nyc @Aqua-Letifer

                        Good job guys!!!

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