Question

Why sand is thrown on the tracks covered with snow?

Answer 1

Friction:

1. The frictional force is generated when two surfaces that are in contact slide over each other.
2. Also, the frictional force presents a great measure of resistance to the relative motion of these surfaces.
3. For example, while cycling, when you stop pedalling a bicycle, it slows down gradually and halts after some time. This is due to friction.
4. Friction can be calculated by $f=\mu N$, where $f$ is the frictional force, $\mu$ is coefficient of friction and $N$ is the normal force.

A diagram to represent friction

Explanation:

1. When tracks are covered with snow, the friction between track and train wheels reduces.
2. This makes the tracks unsafe for driving.
3. So, the friction is increased by throwing snow on the tracks.

Hence, when tracks are covered with snow, they have low friction, and it is impossible to walk. When sand is thrown on tracks, the force of friction is increased.