Physics in Depth

Viscosity The property of a fluid by virtue of which an internal friction comes in to play when the fluid is in motion and opposes the relative motion of its different layers is called viscosity . If we move through a pool of water we experience a resistance to our motion. This shows that there is a frictional force in liquids. We say this is due to the viscosity of the liquid. If the frictional force is comparatively low, as in water, the viscosity of the liquid is low; if the frictional force is large, as in glue or glycerine, the viscosity of the liquid is high. Newton's law of viscosity, Coefficient of viscosity Consider the streamline flow of a liquid as in figure. The layer of liquid in contact with the fixed horizontal surface is at rest and all the other layers move parallel to each other with their velocities increasing uniformly upwards. Consider two uppermost layers at a distance x and x+dx from the horizontal surface with v and v+dv...

Intermolecular forces : Origin and its types Forces that exists between molecules either of same types or different types within the molecular range are called the intermolecular forces . Intermolecular forces arises from two main causes: Potential energy of the molecules (due to the interactions between surrounding molecules-principally electrical in origin). Thermal energy of the molecules ( i.e., kinetic energy of the molecules): Depends on the substance concerned. Intermolecular forces are of two types: Force of cohesion and Force of Adhesion . Force of cohesion is the force of attraction between the molecules of the same substance. Example: coalescion of two water drops into a single when brought together. Force of adhesion is the force of attraction between the molecules of the different substances. Example: adhesive force between clean water and glass wets the glass plate when water is poured on it. Image source CAWater-info Energy ...

Fluid is a substance that can flow. Fluids take the shape of a container on which we put them. Fluid flows because they cannot withstand the shearing stress (i.e., tangential force per unit area ). However, it can exert a force in the direction perpendiular to its surface. Liquids and gases are fluids. Some characteristics properties of a fluid can be described by its density and pressure. Density Density of a substance is defined as the ratio of mass per unit volume. \[\rho=\frac{m}{V}\] Here, \(\rho\) is the density of the substance with mass m and volume V . Density is a scalar quantity and its SI unit is \(kg/m^3\). Pressure Pressure is defined as the force per unit area. \[P=\frac{F}{A}\] Here, F is the magnitude of normal force on area A . Pressure is a scalar quantity and its SI unit is \(N/m^2\) or Pa (Pascal). Pressure exerted by a liquid at a depth h is, \[P=h\rho g\] Here, \(\rho\) is the density of liquid and g is the acceleration d...

Periodic Motion When a body repeats its motion after regular time intervals we say it is in periodic motion . The time interval after which the motion is repeated is called the time period . If a body moves to and fro on the same path, it is said to perform oscillations . Every oscillatory motion continues due to the interaction of inertia and elasticity . Cause of oscillatory motion When an oscillator is displaced from its postion of equilibrium by application of a force and thus doing work on it, a restoring force comes into play tending to bring it back to its equilibrium position. According to Hooke's Law, this restoring force is proportional to the displacement and depends upon the elasticity of the system. As soon as the restoring force tries to bring the system back to its equilibrium position, the property of inertia opposes this change in velocity. Further, when the system reaches the equilibrium position, it overshoots the mark and m...

ENTANGLEMENT · TELEPORTATION · PHYSICS Nothing travels between them. Two particles, once linked, keep answering for each other — no matter how far apart you pull them. ↑ ↓ STATE Δt = — ms Flip either particle. Drag one across the box first if you like — the other still answers instantly, at any distance. 01 — THE ENTANGLED PAIR Two particles, one behavior. When certain quantum particles are created together, they can end up entangled — bound to each other in a way that survives even enormous separation. Measure one particle and it settles into a definite state. The instant that happens, its partner's state is settled too — even if it's sitting on the other side of a room, a continent, or an orbiting satellite. It's less like sending a signal from one to th...