A body of weight 20N is on a horizontal surface, minimum force applied to pull it when applied force makes an angle 600  with horizontal (angle of friction μ=300 ) and acceleration is

Fcosθ=μ(mg−Fsinθ)               F×12=13[20−F32]               F2=203−F2               F=203N               It is the force required to move the block with  uniform velocity               ∴  acceleration = 0