If is painful to walk barefooted on the ground covered with edged pebbles. Why?

Why it is painful to walk barefooted on the floor covered with edge pebbles?

Send is spread on tracks covered with snow. Why ?

Why is it difficult to walk on sand?

Why is it difficult to walk on sand?

A speed ramp at an airport is a moving conveyor belt on which you can either stand or walk. It is intended to get you from place to place more quickly. Suppose a speed ramp is 120 m long. When you walk at a comfortable speed on the ground, you cover this distance in 86 s. When you walk on the speed ramp at this same comfortable speed, you cover this distance in 35 s. Determine the speed at which the speed ramp is moving relative to the ground.

Why is it dificult to walk on solid ice?

Raman was surprised to see a camel walking easily barefooted on sand but he himself was unable to walk barefoot on sand. What is the reason behind this?