WAEC 2019 · Paper 2 · Q5

Statics: forces, equilibrium & moments

(a)
Three forces $10\text{ N}$ , $14\text{ N}$ and $16\text{ N}$ acting on a particle keep it in equilibrium. Find the angle between the forces $10\text{ N}$ and $16\text{ N}$ .

Worked solution (try it first)

The 10 N and 16 N forces have a resultant of 14 N, balancing the third force.
$14^2 = 10^2 + 16^2 + 2(10)(16)\cos\theta$ , so $196 = 356 + 320\cos\theta$ .
$\cos\theta = -\dfrac{160}{320}$
$= -\dfrac12$ , so $\theta = 120^\circ$ .

Report a problem with this question