# vector question help!! (1 Viewer)

#### poptarts12345

##### Member
Two forces, of magnitude p newtons and q newtons, have a resultant of 2√7 N when they act at 90° to each other. When they act at 30° to each other, however, the magnitude of the resultant is 2√13 N. Find the values of p and q.

This question is from the cambridge textbook.

ANS : 2√3 and 4

#### Trebla

##### Administrator
Administrator
When they are at right angles you will get

$\bg_white p^2+q^2=28$

When they are at 30 degrees with each other, note that the resultant vector is the diagonal of a parallelogram which has sides p and q. You can then use the cosine rule to get

$\bg_white pq=8\sqrt{3}$