JEE : Force

If 3 Forces can be represented by sides of a triangle, then they are said to be in equilibrium ; i.e. their resultant is 0.

According to Lami's Theorem ; F1 / sin α = F2 / sinβ = F3/ sin γ  ( For forces in equilibrium) 1) If lift is moving upward, the weight of object is added to the Force exerted by lift . mg + ma

2) If the lift is stationary or in state of uniform motion, then the weight of the object is the only force acting on it

3) If the lift is moving down, the weight of the object is subtracted  by the Force exerted by the lift . mg - ma

4) If a > g ; then the body will rise and stick to the ceiling of the lift . Inclined Plane :-

a = g sinθ (vertical)

A = g tanθ (horizontal)

Blocks over Pulley :-

T = g [ 2m1m2 / m1 + m2]