Chapter 12 Thermodynamics
ZEROTH LAW OF THERMODYNAMICS
This law states that ‘two systems in thermal equilibrium with a third system are in thermal equilibrium with each other.
THE FIRST LAW OF THERMODYNAMICS
It is the general law of conservation energy applied to any system in which energy transfer from or to the surroundings (through heat and work) is taken into account.
THE SECOND LAW OF THERMODYNAMICS
Kelvin-Planck statement: No process is possible whose sole result is the absorption of heat from a reservoir and complete conversion of heat into work.
Clausius statement: No process is possible whose sole result is the transfer of heat from a colder object to a hotter object.
It implies that no heat engine can have efficiency equal to 1 or no refrigerator can have co-efficient of performance equal to infinity.
A process is reversible if it can be reversed such that both the system and the surroundings return to their original states, with no change anywhere else in the universe. Spontaneous processes of nature are irreversible.
Carnot’s engine is a reversible engine operating between two temperatures T1 (source) and T2 (sink). The Carnot cycle consists of two isothermal processes connected by two adiabatic processes.
No engine operating between two temperatures can have efficiency greater than that of a Carnot engine.
If Q > 0, heat is added to the system
If Q < 0, heat is removed from the system
If W > 0, work is done by the system
If W < 0, work is done by the system
Chapter 10 Mechanical Properties Of Fluids
Pressure is defined as the normal force acting per unit area.
P = F/A
Pressure is a scalar quantity.
Pascal’s law states that pressure in a fluid at rest is same at all points which are at the same height.
The pressure in a fluid varies with depth h according to the expression:
P = P0 + ρgh, where ρ is the density of the liquid
It states that as we move along a streamline, the sum of the pressure and the kinetic energy per unit volume remains constant.
Surface tension is a force per unit length (or surface energy per unit area) acting in the plane of interface between the liquid and the bounding surface.
Chapter 9 Mechanical Properties Of Solids
Elasticity is a property by the virtue of which the solid regains its original shape once the external force is removed.
Plasticity is the property by virtue of which the sold does not regain its original shape even after all the external forces are removed.
Ductility is the property of a solid to be drawn into thin wires.
Malleability is the property of a solid to be beaten into thin sheets.
Stress is the restoring force per unit area. When we apply an external force on the body to change its shape there is a restoring force that develops in the body in the opposite direction.
Mathematically, Stress = F / A, where F is the restoring force that develops in the body and A is the area. The SI unit of stress is N/m2 or Pascal (Pa).
Types of stress:
Strain is a measure of deformation i.e. the displacement between the particles in the body.
Mathematically, Strain= (Change in length)/ (original length)
Types of strain:
This law states that within the elastic limit, stress developed is directly proportional to the strain produced in a body.
Stress = k x strain, where k is the modulus of elasticity
Elastic modulus: It is the ratio of stress and strain.
Chapter 7 System Of Particles And Rotational Motion
In a rotation of a rigid body about a fixed axis, every particle of the body moves in a circle, which lies in a plane perpendicular to the axis and has its centre on the axis.
CENTRE OF MASS
The centre of mass is taken to be a single point at which the entire mass of the system is concentrated and all the applied forces act at that point.
MOTION OF CENTRE OF MASS
The centre of mass of a system of particles moves as if all the mass of the system was concentrated at the centre of mass and all the external forces were applied at that point.
LINEAR MOMENTUM OF A SYSTEM OF PARTICLES
The total momentum of a system of particles is equal to the product of the total mass of the system and the velocity of its centre of mass.
A pair of equal and opposite forces with different lines of action is known as a couple.
CENTRE OF GRAVITY
The centre of gravity of an object is the point at which weight is evenly dispersed and all sides are in balance.
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