1-6 Drawing forces

Drawing forces (p. 16)
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Drawing forces (p. 16)
Bluetooth 
- ON
- VPN off

Stationary
- Writingbook
- Pen, pencil
- Calclator
- iPad

Mark
- NO


Lessonup
- YES
schoolbags in
the cupboard
Phones in the phone bag

Slide 1 - Diapositive

Lesson goals:
  • Draw or sketch a force diagram when forces work in different directions. 
  • Calculate the direction of the
        resultant force using trigonometry.

Slide 2 - Diapositive

Vector
A vector has magnitude, 
direction and a point of application.

We draw a vector with an arrow:
  • The length of the arrow indicates the size of the force.
  • The direction of the arrow indicates the direction of the force.
  • The place where the arrow begint indicated the point of application of the force.

    Slide 3 - Diapositive

    Resultant force
    The sum of all te forces.
    Also called: nett force or sum force.
    (Fr)

    Slide 4 - Diapositive

    Steps for drawing a vector diagram
    Step 1 - Choose a scale
                             (e.g. 1 cm = 5N, so 15 N = 3 cm)
    Step2 – Think about the point of application and the direction.
    Stap 3 – Draw the force 
                      Example: Draw a force of 60N to the right. 
                      Scale 1cm = 10 N

    Slide 5 - Diapositive

    Forces acting in the same direction...
    are added together.

    Slide 6 - Diapositive

    Forces acting in opposite direction...
    are subtracted.

    Slide 7 - Diapositive

    Equilibrium
    When two equal forces act in opposite directions. For example, a book that lies on a table.
    Normal 
    When forces are in equilibrium we say the resultant force 
    equals 0N
    (Fr)

    Slide 8 - Diapositive

    Combining forces
    • Sometimes you have forces acting 
          in different diractions.
    • In this case you get the resultant 
          force by combining the forces. 
    • Both the size and magnitude of the resultant force is important in your answer.

      Slide 9 - Diapositive

      Parallelogram method
      1. Choose an appropriate scale.
      2. Draw the forces on scale using the given angle (like two adjacent sides of a parallelogram).
      3. Complete the parallelogram.
      4. Draw an arrow from the starting point to the opposite corner of the parallelogram.  
      5. Measure the length of the arrow, give magnitude and direction.

      Slide 10 - Diapositive

      Example from the book (p. 17)

      Slide 11 - Diapositive

      Maak opgaven 22 (p. 19)
      timer
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      Slide 13 - Diapositive

      Maak opgaven 23 (p. 19)
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      3:30

      Slide 14 - Diapositive

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      Maak opgaven 24 (p. 19)
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      3:30

      Slide 16 - Diapositive

      Slide 17 - Diapositive

      Perpendicular forces
      When two forces are acting perpendicular to each other, you can calculate the resultant force with pythagoras.
      Fres=302+402
      =50N

      Slide 18 - Diapositive

      Perpendicular forces
      You can then calcualtet he angle of the resultant force using
      tan(α)=F2F1

      Slide 19 - Diapositive

      Homework
      Test yourself 1.2

      Slide 20 - Diapositive

      What did you
      learn today?

      Slide 21 - Carte mentale

      Conclusion:
      When forces act in different directions 
      you have to combine the forces.
      You can use the parallelogram method.
      When the forces at at an angle of 90 degrees then you can calculate the unknown side using pythagors.


      Slide 22 - Diapositive