Everything Science Grade 11

CHAPTER 11. VECTORS 11.7

Let us draw F 1 first. According to the scale it has length 5 cm.

5 cm

Step 4 : Draw the second scaled vector

Next we draw F 2. According to the scaleit has length 4 cm. Wemake use of a

protractor to draw this vector at 30◦to the horizontal.

5 cm = 5 N

4 cm = 4 N

30 ◦

Step 5 : Determine the resultant vector

Next we complete the parallelogram and draw the diagonal.

5 N

4 N Resultant

?

The resultant has a measured length of 8,7 cm.

Step 6 : Find the direction

We use a protractor to measure the angle between the horizontal and theresul-

tant. We get 13,3◦.

Step 7 : Apply the scale conversion

Finally we use the scaleto convert the measuredlength into the actual magni-

tude. Since 1 cm = 1 N, 8,7 cm represents 8,7N. Therefore the resultant force

is 8,7 N at 13,3◦above the horizontal.

The parallelogram method is restricted to the addition of just two vectors. However, it is arguably the
most intuitive way of adding two forces acting on a point.

Algebraic Addition andSubtraction of Vec-

tors

ESBEL

Vectors in a Straight Line

Whenever you are facedwith adding vectors acting in a straight line (i.e.some directed left and some
right, or some acting upand others down) you can use a very simple algebraic technique: