Question

the resultant of two forces of magnitude 10N each has also magnitude of 10N.the angle between the forces is?
(a) o
(b)90
(c)180
(d)120

Answer 1

It is an equal lateral triangle therefore each angle is equal to 60 degrees. So does that mean the total of the three which means 180?

Answer 2

the angle between them will be 120.Let me explain .resultant of two vectors A and B is given as:
R=\[\sqrt{A ^{2}+B ^{2}+2ABcos \theta}\]
cos 120=-1/2.so in this case,
R=\[\sqrt{10^{2}+10^{2}-2\times\ 10 \times10\times1/2}\].which gives R=10.