Slow moving vehicles must display emblem at the rear to warn of their low speed.

Reflective emblem

Explanation:

A slow moving vehicle must display a reflective emblem at the rear to warn of their low speed. The sign of emblem is triangular in shape indicating that any sad incident have happened. Slow moving vehicles are generally prone to accident because of low visibility so they must display reflective emblem at rear.

electric field is a function of 1/r^2

yes, the force per unit charge for a point charge is inverse square law.