IIT JEE Advanced 2008 Paper 2

Case 1: For pulling an object, we have
N + Fsinθ = mg
⇒ N = mg – Fsinθ

Case 2: For pushing an object, we have
N′ = Fsinθ + mg > N
f ′ = μN′ > f = μN

Hence, it is easier to pull than to push an object from level ground; the force (f) depends on the nature of surfaces in contact.