Answer:
(a) When the resultant force is pointing along east line, the magnitude and direction of the second force is 280 N East
(b) When the resultant force is pointing along west line, the magnitude and direction of the second force is 560 N West
Explanation:
Given;
a force vector points due east, [tex]F_1[/tex] = 140 N
let the second force = [tex]F_2[/tex]
let the resultant of the two vectors = F
(a) When the resultant force is pointing along east line
the second force must be pointing due east
[tex]F = F_1 + F_2\\\\F_2 = F - F_1\\\\F_2 = 420 \ N - 140 \ N\\\\F_2 = 280 \ N[/tex]
[tex]F_2 = 280 \ East[/tex]
(b) When the resultant force is pointing along west line
the second force must be pointing due west and it must have a greater magnitude compared to the first force in order to have a resultant in west line.
[tex]F = F_2 - F_1\\\\F_2 = F + F_1\\\\F_2 = 420 \ N + 140 \ N\\\\F_2 = 560 \ N[/tex]
[tex]F_2 = 560 \ West[/tex]