1-6 Drawing forces

Lesson goals:
  • Draw or sketch a force diagram when forces work in different directions. 
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Slide 1: Slide
NatuurkundeMiddelbare schoolvwoLeerjaar 3

This lesson contains 22 slides, with interactive quiz and text slides.

time-iconLesson duration is: 50 min

Items in this lesson

Lesson goals:
  • Draw or sketch a force diagram when forces work in different directions. 

Slide 1 - Slide

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 2 - Slide

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

    Slide 3 - Slide

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

    Slide 4 - Slide

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

    Slide 5 - Slide

    Forces acting in opposite direction...
    are subtracted.

    Slide 6 - Slide

    do the exercises 13 to 21

    Slide 7 - Slide

    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 8 - Slide

      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 9 - Slide

      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 - Slide

      Example from the book (p. 17)

      Slide 11 - Slide

      Do exercise 22 (p. 19)

      Slide 12 - Slide

      Slide 13 - Slide

      Do exercise 23 (p. 19)

      Slide 14 - Slide

      Slide 15 - Slide

      Do exercise 24 (p. 19)

      Slide 16 - Slide

      Slide 17 - Slide

      Perpendicular forces
      When two forces are acting perpendicular to each other, you can calculate the resultant force with pythagoras.

      Slide 18 - Slide

      Perpendicular forces
      You can then calcualtet he angle of the resultant force using

      Slide 19 - Slide

      Test yourself 1.2

      Slide 20 - Slide

      What did you
      learn today?

      Slide 21 - Mind map

      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 - Slide