Practice MCQ Questions and answers on Physics-GK

Capillary action is the result of adhesion and surface tension. Adhesion of water to the walls of a vessel will cause an upward force on the liquid at the edges and result in a meniscus which turns upward. The surface tension acts to hold the surface intact, so instead of just the edges moving upward, the whole liquid surface is dragged upward.

A liquid disturbed by stirring comes to rest due to viscosity.

The water rise in a capillary tube dipped in water is such that the weight of water in the tube above the surface of water in the vessel is equal to (balances) the upward force due to surface tension. So it is clear that if the the bore (radius) to the tube is decreased, the height of the water column in it must be greater. So, (a) is correct

It is because of the capillary action phenomenon because of which oil rise up the wick in a lamp. Capillary action, or capillarity, is the ability of a liquid to flow in narrow spaces without the assistance of, and in opposition to external forces like gravity. The effect can be seen in the drawing up of liquids between the hairs of a paint-brush, in a thin tube, in porous materials such as paper, in some non-porous materials such as liquefied carbon fiber, or in a cell. It occurs because of inter-molecular attractive forces between the liquid and solid surrounding surfaces.

If r1 is the density of the lead piece of volume v, the volume of water displaced by the ice block and the lead piece while floating is Vw = (V–v) r1 + v r1. When the ice melts, the lead piece sinks in water since r1 is greater than the density of water. The water produced by the melted ice has the volume (V-v) r1 and the volume displaced by the lead piece is v. So, the total volume of the water produced by ice and that displaced by the lead piece is V w1 = (V–v) r1+ v r1< V w. So, the water level goes down.

When detergent is added to water, it decreases the surface tension of the water. Compounds that lower water's surface tension are called surfactants, which work by separating the water molecules from one another.

Due to the lightness of the gas bubble they feel less centrifugal force so they get collected near the neck of the bottle. They collect near the center of circular motion i.e. near the neck of the bottle.

A fluid with large viscosity hinders motion because its molecular makeup gives it a lot of internal friction. Oil is the most viscous amongst all the option.

Raindrops start to form in a roughly spherical structure due to the surface tension of water. This surface tension is the "skin" of a body of water that makes the molecules stick together. The cause is the weak hydrogen bonds that occur between water molecules.

The fact that two large ships travelling on close parallel courses in the same direction tend to move towards each other can be explained by Bernoulli's principle. The rapid flow of air between the two moving ships causes a reducton of pressure (Bernoulli's principle) , so they (the ships) are drawn closer together.