Question

If you try to hold a glass with oil on your hands, it tends to slip. Why?

Answer 1

1. When we hold something, then the force of friction will work on the object (here object is glass) and our hand, to hold the glass from falling.
2. However, when we hold the glass with an oily hand then it will slip out because the oil is a lubricant that reduces the friction between the glass and our hand.