Hydraulic Advantage by qingyunliuliu


									Hydraulic Advantage
    What is the advantage of Hydraulics
    Calculating MA, SR, and E
Calculating Hydraulic Advantage
   There is a mechanical advantage when
    using hydraulics to lift a load
   We calculate this advantage using the
    same formulas that we have used in the

    MA = Foutput   SR = dinput    E = MA x 100
         F input        doutput       SR
Hydraulic Lifting Devices

   Input                    Output
   piston…                  piston…
   Input                    Output
   Force and                Force and
   Distance                 Distance
Hydraulic Lifting Devices
   Hydraulic lifting devices have an input
    piston for the input force and output
    piston for the output force

   Calculating MA, SR and E all depend on
    the Surface Area Ratio (SAR)

   The ratio in size difference between the
    two pistons will determine the MA and SR
    Hydraulic Lifting Devices
   If we have a small area making up the input piston
    which has an area of 1 unit of area (1 m²)
   The output piston has an area made up of 9 of the
    same units (9 m²)… Therefore the SAR is 9 because
    the output piston is times larger than the input
                   Small Area
                   for the input
                             Large Area for
                             the output piston
 Hydraulic Lifting Devices
Surface Area Ratio = Area of Large Piston (output)
                      Area of Small Piston (input)
SAR = Area large piston
       Area small piston
SAR = 9 m²
       1 m²
SAR = 9
    Hydraulic Lifting Devices
   Here we have a small 10 N force applied to the
    input piston (1 unit of area or 1 m²)
   The output piston has an area made up of 9 of the
    same units (9 m²)… Therefore we multiply the
    input force by 9 to find out what the output force
    will be

        10 N
 Hydraulic Lifting Devices
 If we apply 10 N of force to the input piston, then we
  need to multiply that by 9 to know what the output
  force is
 Therefore…

Output Force = Input force x Surface Area Ratio
Output Force = Input force x SAR
Output Force = 10 N x 9                                 90 N
Output Force = 90 N
                             10 N
    Hydraulic Lifting Devices
 If we were given the output force and we needed to
  calculate the input force, We would now divide rather
  than multiply because the input force is smaller than
  the output force
 Therefore…
Input Force = Output force x Surface Area Ratio
Input Force = Output force x SAR                    90 N
Input Force = 90 N ÷ 9
Input Force = 10 N           10 N
 Calculating Mechanical Advantage
 We now know that the input force is 10 N and the
  output force is 90N
 Therefore we can now calculate Mechanical

MA = Foutput
MA = 90 N
     10 N
MA = 9
    Hydraulic Lifting Devices
   The disadvantage is that the output distance will
    only be 1/9th our input distance
   We gain Mechanical Advantage, but we lose when
    it comes to Speed Ratio
    Hydraulic Lifting Devices
 If we push down on the input piston for a total
  distance of 18 cm, then the output distance will be
  1/9th of 18 cm
Output distance = Input distance
                   Speed Ratio                     2 cm
Output distance = 18 cm
                   9 cm
                             18 cm
Output distance = 2 cm
 Calculating Speed Ratio
 We now know that the input Distance is 18 cm and
  the output Distance is 2 cm
 Therefore we can now calculate Speed Ratio

SR = dinput
SR = 18 cm
      2 cm
SR = 9
    Surface Area Ratio is the Key!
   As we have now calculated, the MA, SAR and SR
    are all the same
   If you can calculate the surface area of both pistons
    and figure out what the ratio is between them,
    then you automatically know what the MA and SR
    will be
Should we x or ÷
   When deciding whether to
    multiply or divide by the
    SR for MA or SAR… you
    need to visualize the
    system and decide if the
    value you are calculating
    will be less than your
    starting value, or more
   If it should be less, you ÷
   If it should be more, you x
    Example Question (on the board)
   The person exerts a force of 40 N, the car exerts a
    force of 1200 N
   How many times heavier is the car than the
    person? (This is the same as asking what is MA)
   How large would the area of the output piston
    have to be if the in put piston is 0.5 m²
                    N          N
    Example Question (on the board)
   What is the Mechanical Advantage of this
    hydraulic system? What is the Speed ratio of the
   If the Output distance was 0.5 m, then what would
    the input distance be?

                   N         N
    Example Question (on the board)
   What will the pressure in the system be as the
    person is applying her 40 N of force to an area of
    0.5 m²

                    N         N
Hydraulic Demo
   Take a look at the
    two syringes at the
    front of the room
   Make your
    predictions as to what
    will happen in terms
    of input/output force
    and distance
   What will the
    efficiency of this set
    up be (theoretically)
Home Work
   Take some time to look at the worksheet
    and practice some of the example questions
   This sheet will be marked in class so if you
    are having troubles, make sure you ask for
    help or come in after school

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