Answer:
4.4N, 263.4°
Explanation:
The sum of all forces must add to zero:
The forces in the x-plane:
∑F = 3N + (cos 120°)*5N + x = 0
x = -(3N + (cos 120°)*5N)
x = -0.5N
The forces in the y-plane:
∑F = (sin 120°)*5N + y = 0
y = -(sin 120°)*5N = -√(3/4)*5N = -4.3N
The magnitude of the unknown force U is:
U = √(x² + y²) = √19 = 4.4N
The direction is given by:
tanФ = y/x
Ф = 263.4°