Everything Science Grade 11

11.7 CHAPTER 11. VECTORS

H

3 cm = 6 km

A

6 cm = 12 km B

C

2,25 cm = 5,5 km

? 4,6 cm = 9,2 km

N

S

W E

Step 7 : Apply the scale conversion

We now use the scale toconvert the length of theresultant in the scale diagram

to the actual displacement in the problem. Sincewe have chosen a scaleof 1 cm

= 2 km in this problemthe resultant has a magnitude of 9,2 km. The direction

can be specified in terms of the angle measuredeither as 072,3◦east of north or

on a bearing of 072,3◦.

Step 8 : Quote the final answer

The resultant displacement of the ship is 9,2 kmon a bearing of 072,3◦.

Example 3: Head-to-Tail GraphicalAddition II

QUESTION

A man walks 40 m East,then 30 m North.

1. What was the total distance he walked?


2. What is his resultantdisplacement?

SOLUTION

Step 1 : Draw a rough sketch

resultant

40 m

30 m N

S

W E

Step 2 : Determine the distancethat the man travelled

In the first part of his journey he travelled 40 m and in the second part hetravelled

30 m. This gives us a total distance travelled of40 m + 30 m = 70 m.

Step 3 : Determine his resultant displacement