Define Angle of contact

Hint: Every droplet tries to stay the area to the minimum. surface tension is accountable for the form of liquid droplets. Since surface to volume ratio is minimum for the spherical shape and hence, a liquid drop is spherical in shape. Every liquid drop has its terminal velocity too, terminal velocity is the reason that the liquid drop does not hit us hard when they fall from such a big height up in the sky.

Complete step-by-step solution:
When the liquid is in touch with solid, the angle between the solid surface and therefore the tangent to the free surface of the liquid at the purpose of contact, measured from inside the liquid is named the angle of contact. Each given system has a unique liquid angle which depends on the temperature and pressure of the system and also of the liquid drop or liquid. Both these quantities vary from system to system and hence this is the reason that we have a different contact angle or angle of contact for different systems. When the liquid surface is curved concave upwards, the angle of contact is acute and when the liquid surface is curved convex upwards, the angle of contact is obtuse. Below is the figure showing the acute angle for the angle of contact of a liquid drop.


Note: Surface tension is that the tendency of liquid surfaces to shrink into the minimum area possible. surface tension allows insects to float and slide on a water surface. There are two primary mechanisms in play, The inward force and the tangential force. The combination of these forces results as surface tension of liquid.