靜力學(解答)

1. Resolve the 30N in the direction parallel and perpendicular to the 40N force.
For direction parallel to the 40N force, force componet = 30cos(60) N
For direction perpendicualr to the 40N force, force component = 30.sin(60) N
Hence, sum of force in direction of 40N force = (40 + 30.cos(60)) N = 55 N
force in direction perpendicualr to 40N force = 30.sin(60) N = 25.98 N
Therefore, resultant force = square-root[55^2 + 25.98^2] N = 60.8 N

2. Force difference in direction parallel to 40N force
= [40 - 30.cos(60)] N = 25 N
Therefore, resultant force = square-root[25^2 + 25.98^2] N = 36.1 N