Mechanics question

Hi, can someone explain to me how to do this question step by step?
Thankyou! :smile:

Two forces, (4i – 5j) N and (pi + qj) N, act on a particle P of mass m kg. The resultant of the two forces is R. Given that R acts in a direction which is parallel to the vector (i – 2j),
(a) find the angle between R and the vector j,

(b) show that 2p + q + 3 = 0.

Reply 1

J2JW

Hi
Okay let's see
(a) if R is parallel to (I-2j) it means that velocity of R is k(I-2j).
Try to draw (I-2j) on the axes. You 'll see how it goes and what angle you need to find. The angle can be found by arctan. So arctan of the angle is (2/1). Then calculate bearing. Look how you can achieve this angle from the north. Bearing will be 90+arctan(2/1). That's it, I think. You'd better check the answer! :smile:

B is a bit tougher. Wait a bit

Btw are you preparing for mock or why?