Question

Find the resultant of forces 3N and 4N acting at right angles to each other ​

Answer 1

Answer:

The Resultant of vectors perpendicular to each other can be solved in two ways:

Method one: Pythagoras Theorem

a2 + b2 = c2

In the case of vectors c is replaced by the resultant R

a2 + b2 = R2

3^2 + 4^2 = R2

9 + 16 = R2

25 = R2

R = 5N

Method two: cosine rule

R2 = a2 + b2 + 2*a*b*cosα

Where R is resultant and α represents the angle between vectors a and b.

R2 = 3^2 + 4^2 + 2*3*4*cos90

R2 = 9 + 16 + 0

R2 = 25

Take the square root of both sides

R = 5N

For any other angle other than 90°, I suggest to use only the second method, the cosine rule.