Walking on ice

Question:

Why it is difficult to walk on an ice covered road?

Answer:

When you are standing still on a surface – ice, grass, sand, tarmac, road etc there are two equal and opposite forces acting.
(a) the downwards force of you on the road – your weight (vertical red arrow) and
(b) the upward force of the road on you (vertical blue arrow)

There is no resultant force and so you stand still.

When you want to walk forward you have to lean forward. As soon as you do this you are applying a backwards force on the surface (horizontal blue arrow) on which you are standing as well as the downwards force due to your weight.

The surface exerts and equal and opposite force on you and it is this force that enables you to move forwards (horizontal red arrow).

Now if there is very low friction between your feet (or shoes) and the surface you can't apply much backwards force before your foot starts to slip. This means that the surface cannot apply much forwards force on you and so you won't be able to move forwards.

Icy roads have very low friction and so can't apply much force on you before you slip and so it is difficult to walk.