05-01-2018, 04:28 PM
*SI (System International) is the modified form of MKS System.
*SI system is the globally approved form of unit system.
*Unit of Distance - Parsec (Parsec is a Light Year Distance Unit)
*1 Parsec = 3.26 light year
*Plane angle -Radian (rad)
*Solid angle -Steradian (Sr)
*Temperature -Degree Celsius (°C)
*Energy, Work, Heat -Joule (J)
*Force -Newton (N)
*Power, Radiant flux -Watt (W)
*Illuminance -Lux (lx)
*Electric charge -Coulomb ©
*Resistance -Ohm (Q)
*Conductance -Siemens (S)
*Capacitance -Farad (F.)
*Inductance -Henry (H)
*Pressure, Stress -Pascal (Pa)
*Magnetic flux -Weber (Wb)
*Radioactivity -Becquerel (Bq)
*Frequency -Hertz (Hz)
*Electric Potential Difference, EMF- Volt (V)
*Magnetic flux density-Tesla (T)
*Luminous flux -Lumen (lm)
*Catalytic activity -Katal (Kat)
Derived Units
*Derived Units are the units which are derived from the fundamental units.
eg: Speed, Area, Acceleration etc.
*In general, Physical quantities are divided into two classes.
1.Scalar quantities 2. Vector quantities
*A physical quantity that has only magnitude, but no direction is known as - Scalar quantity eg: Mass, Length, Time, Volume, Speed, Energy, Work, Pressure, Density etc.
*A physical quantity that has both magnitude and direction is known as - Vector quantity eg: Velocity, Momentum, Force, Acceleration, Displacement, Torque etc.
Work, Energy, Power
Work
*A work is said to be done if there is a displacement of the body on which force is acted, in the direction of the force applied.
*The work done by a force is given by area of force-displacement graph.
*A man pushes a metal block and fails to it He does - no work at all
*W = Fxd
‘F’ - Force applied
'd’ - Distance which object is displaced
‘W' -'Work done by the force
Energy
*Ability of a body to do work - Energy Unit of work: Joule or Nm (Newton metre)
*In CGS, the unit of work is erg 1 Joule = 107erg
*The term ‘Energy’ was first coined by - Thomas Young.
Albert Einstein
*Law of Conservation of Energy was put forwar d by
Ans : Albert Einstein.
*According to law of conservation of energy, energy can neither be created nor be destroyed but can be transformed from one form to another.
*Einstein proposed special theory of Relativity in 1905.
*Einstein proposed General theory of relativity in 1915.
*E = mc2 is known as the mass - energy equivalence which shows the relation between matter and energy.
Potential Energy & Kinetic Energy
*Energy of an object occurred due to its motion
Ans : Mechanical energy
*Mechanical energy is of two forms,
1. Potential energy 2. Kinetic energy
*The energy possessed by a body by virtue of its position is
Ans : Potential Energy (P.E).
*For a body of mass ‘m’ situated at a height ‘h’ above the ground, P.E. = mgh
‘g' federation due to gravity.
m - mass
h-height
*Energy stored in the water-reservoir of a dam
Ans : Potential energy
*Energy stored in a compressed spring
Ans : Potential energy
*Potential energy of an object at rest on ground
Ans : Zero
*Potential energy increases as the height
Ans : increases.
*For an object thrown vertically upwards potential energy increases and kinetic energy decreases.
*Potential energy of an object will always be possessed above the level of earth’s surface. For a freely falling object potential energy decreases as it approaches earth.
*The energy possessed by a body due to its motion is
Ans : Kinetic Energy (K.E.)
*For a body of mass ‘m’ moving with a velocity V, K.E. = V2 mv2 m = mass, v = velocity
*If the velocity of an object is doubled, its kinetic energy becomes four times.
*If the mass of a moving body is doubled, its Kinetic energy is also doubled.
*A moving bullet or a moving stone possesses Kinejic energy.
*Kinetic energy is always positive.
*Law of conservation of momentum is used in the application of rocket propulsion, jet engine, firing of a pistol etc.
