Short Answer 
To create an accurate force diagram, start by converting each force’s magnitude into lengths using a scale (1 cm = 40 N). Draw the lines representing the forces according to their calculated lengths and correct orientations, using tools such as a ruler and protractor for precision to ensure proper angles.
Step 1: Convert Forces to Lengths
To accurately represent the forces, start by converting the magnitudes of each force into lengths using a scale where 1 cm equals 40 N. For each force, divide its magnitude by the scale factor to find its length in centimeters. This calculation will provide you with the precise length needed to draw each force’s representation.
- 20 N: 20 N / 40 N/cm = 0.5 cm
- 100 N: 100 N / 40 N/cm = 2.5 cm
- 120 N: 120 N / 40 N/cm = 3.0 cm
- 85 N: 85 N / 40 N/cm = 2.125 cm
- 180 N: 180 N / 40 N/cm = 4.5 cm
Step 2: Draw the Forces
Once you have the lengths calculated, proceed to draw the lines representing each force. Ensure that each line’s length corresponds to the calculated centimeter value and extends in the correct direction according to the force’s orientation. Use a ruler for accuracy when drawing each line.
- Draw 0.5 cm east for 20 N
- Draw 2.5 cm west for 100 N
- Draw 3.0 cm southeast for 120 N
- Draw 2.125 cm north for 85 N
- Draw 4.5 cm northwest for 180 N
Step 3: Ensure Proper Angles
For lines that are not aligned with cardinal directions (like southeast or northwest), use a protractor to achieve correct angles. Remember that southeast is at a 45° angle between south and east, while northwest is at a similar angle between north and west. With the right tools and techniques, your force diagram will accurately represent the forces at play.