FOLLOW US ON TWITTER
SHARE THIS PAGE ON FACEBOOK, TWITTER, WHATSAPP ... USING THE BUTTONS ON THE LEFT


YOUR PARTICIPATION FOR THE GROWTH OF PHYSICS REFERENCE BLOG

Sunday, May 10, 2020

Two forces, each of 10 N, act at a point P as shown in the diagram. The angle between the directions of the forces is 120°.


Question 16
Two forces, each of 10 N, act at a point P as shown in the diagram. The angle between the directions of the forces is 120°.

What is the magnitude of the resultant force?
A 5N                B 10N              C 17N              D 20N





Reference: Past Exam Paper – June 2003 Paper 1 Q3





Solution:
Answer: B. 

Since the angle on the right of the diagonal vector is 120° with the horizontal, the angle on the LEFT of the diagonal vector is 180° – 120° = 60°with the horizontal.


Consider the resultant vector.

Since the 2 vectors given are of the same magnitude, we can assume that the triangle formed when the resultant is formed will at least be an isosceles triangle – that is, the angle that these 2 vectors make with the resultant vector will have the same value. Let this angle be x.

Sum of angles in a triangle is 180°.
60° + x + x = 180°
Angle x = (180° – 60°) / 2 = 60°

Since all the angles are equal in the triangle, it is actually an equilateral triangle. So, the sides will have the same magnitude.
Thus, resultant vector = 10N

The question can also be tackled using sine or cosine rule (depending on the values available).

No comments:

Post a Comment

If it's a past exam question, do not include links to the paper. Only the reference.
Comments will only be published after moderation

Currently Viewing: Physics Reference | Two forces, each of 10 N, act at a point P as shown in the diagram. The angle between the directions of the forces is 120°.