# Maths M1 Mechanics RESOLVING FORCES

• May 8th 2008, 02:10 PM
languages
Maths M1 Mechanics RESOLVING FORCES
Please can someone help me on this question:

Two forces of magnitude 5N and 6N act on the point 0. The angle between the two forces is X

The resultant of the two forces has magnitude 5N.

Calculate the value of X.

Many thanks,
languages
• May 8th 2008, 02:25 PM
icemanfan
Quote:

Originally Posted by languages
Please can someone help me on this question:

Two forces of magnitude 5N and 6N act on the point 0. The angle between the two forces is X

The resultant of the two forces has magnitude 5N.

Calculate the value of X.

Many thanks,
languages

This is basic law of cosines: $\displaystyle c^2 = a^2 + b^2 - 2ab \cos C$

so you have

$\displaystyle 5^2 = 5^2 + 6^2 - 2(5)(6) \cos C$

$\displaystyle 0 = 36 - 60 \cos C$

$\displaystyle 60 \cos C = 36$

$\displaystyle \cos C = \frac{36}{60}$

$\displaystyle \cos C = \frac{3}{5}$
• May 8th 2008, 02:29 PM
languages
Many thanks iceman fan!