4. Resolving Forces

Question 1

Lami’s Theorem

Answer 1

• For any set of three forces P,Q and R in equilibrium
• P / sin α = Q / sin β = R / sin γ

Question 2

Methods of working out forces in equilibrium

Answer 2

• Construct a triangle and work out forces
• Resolve forces in x and y directions; sum of each = 0

Question 3

Forces in equilibrium

Answer 3

resultant = 0

Question 4

If force F makes an angle θ with a given direction, the
effect of the force in that direction is F cos θ

Answer 4

• F cos(90 − θ) = F sin θ
• F sin (90 − θ) = F cos θ