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Whos a physics genius? Two questions regarding Work/Energy

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    Whos a physics genius? Two questions regarding Work/Energy

    A swing is made from a rope that will tolerate a maximum tension of 800N without breaking. Initially, the swing hangs vertically. The swing is then pulled back at an angle of 60.0° with respect to the vertical and released from rest. What is the mass of the heaviest person who can ride the swing?

    In 2.0 minutes, a ski lift raises four skiers at constant speed to a height of 140 m. The average mass of each skier is 65 kg. What is the average power provided by the tension in the cable pulling the lift?

    #2
    Re: Whos a physics genius? Two questions regarding Work/Energy

    Originally posted by vaxopy
    A swing is made from a rope that will tolerate a maximum tension of without breaking. Initially, the swing hangs vertically. The swing is then pulled back at an angle of 60.0° with respect to the vertical and released from rest. What is the mass of the heaviest person who can ride the swing?
    depends on the maximum tension of the rope

    Comment


      #3
      Re: Re: Whos a physics genius? Two questions regarding Work/Energy

      Originally posted by willhaven
      depends on the maximum tension of the rope
      800N - question fixed

      Comment


        #4
        stop sleeping in class
        if you have questions ask your teacher,dont just ask ppl to answer them for you.

        Comment


          #5
          A train sets off for New Orleans from San Antonio at 14:00 and accelerates to 70 MPH. Vaxopy starts off from New Orleans at 14:30 and runs along the tracks towards San Antonio at 7 MPH. How long does he have left to live?

          Comment


            #6
            Originally posted by Mr. Brownstone
            A train sets off for New Orleans from San Antonio at 14:00 and accelerates to 70 MPH. Vaxopy starts off from New Orleans at 14:30 and runs along the tracks towards San Antonio at 7 MPH. How long does he have left to live?
            Originally posted by If you see kay
            stop sleeping in class
            if you have questions ask your teacher,dont just ask ppl to answer them for you.
            an "I dont know" would suffice =)

            Comment


              #7
              You’re better off going to the Ask Jeeves forum or something. I just did a search on your nick, and out of your 16 posts in this community only 4 of them were on-topic. This isn’t the place to ask for help on homework.

              Comment


                #8

                Comment


                  #9
                  i dont' wanna get out no paper to figure out teh swing problem...but the ski lift should be:

                  Work = force * distance / time

                  so work = (65kg * 9.81 m/s^2) * 140 m / 120 sec

                  work = ~744 N*m/s

                  Comment


                    #10
                    A swing is made from a rope that will tolerate a maximum tension of 800N without breaking. Initially, the swing hangs vertically. The swing is then pulled back at an angle of 60.0° with respect to the vertical and released from rest. What is the mass of the heaviest person who can ride the swing?

                    In 2.0 minutes, a ski lift raises four skiers at constant speed to a height of 140 m. The average mass of each skier is 65 kg. What is the average power provided by the tension in the cable pulling the lift?
                    2 weeks

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                      #11
                      I took AP Physics last year, but I forget a lot of the stuff. For the rope... don't you need length, or something also? I am pretty sure it depends how long it is.

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                        #12
                        The answers are

                        1) 40.8kg
                        2)3.0 × 10^3 W

                        so far no one has been right

                        anyone know how to get these answers based on the question?

                        Comment


                          #13
                          are you pop quizing us?

                          Comment


                            #14
                            Maximum force on the rope is in vertical position so the calculation is for that spot.

                            (1) F=Fg+Fcp=mg+mv^2/r=800N max

                            Preservation of energy: g=10m/s^2
                            (2) mgh=mv^2/2

                            Geometry: h - height of the mas in rest.
                            (3) cos60=(r-h)/r ---> h=r(1-cos60)

                            (3)--->(2)

                            (4) mgr(1-cos60)=mv^2/2 ---> v^2/r=2g(1-cos60)

                            (4)--->(1)

                            mg+m2g(1-cos60)=800N --->m=800/(((1+2(1-cos60))g)=40Kg

                            Comment


                              #15
                              Well, cos(60) is .5

                              So, the tension in the vertical direction is actually 400N.

                              Remember, F=ma, so 400 = m * 9.8 (<-- acceleration of gravity). So 400/9.8 = 40.8 kg.


                              For the ski lift, the work done is independent of the path taken, and it's mgh (the potential energy).

                              So mgh for each skier is 65 * 9.8 *140 = 89180.

                              Multiply that out for 4 skiers and it's 356720.

                              Now Power = work/time, and the time is 120 seconds.

                              356720/120 = 2972.67 = 2.972 x 10^3 ~ 3.0 x 10^3 Watts.

                              Hope that helps

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