^Rotational motion
^Rotational motion
Posts
^Sources of error
Sources of error
- The jockey should not be rubbed on the wire, as this resistance of wire will not remain uniform.
- Current should not be allowed to flow in the wire for a long time as this by producing heat will change the resistance of the wire.
- The value of resistor R is so selected that the null point is in the middle of the wire. Actually by doing so the error in the measurement is minimized. Also then all the four resistors are of the same order.
^Rest & motion
^Rest & motion
If position of body changes w.r.t. surroundings with the time then it is said to be moving otherwise at rest. Rest & motion are relative. A person sitting in a moving vehicle is at rest w.r.t. other persons in sitting same vehicle while is in motion w.r.t. other persons standing on road. If the position of a body doesn’t change with respect to all objects in the universe, then it is said to be in absolute rest. Absolute rest is impossible. If the position of a body doesn’t change with respect to one or more things in the universe, then it is said to be in relative rest. Relative rest is possible.
^Astronomical Unit (AU)
^Astronomical Unit (AU)
It is the mean distance of the Earth from the Sun.
1 AU = 1.496 x 1011 m » 1.5 x 1011 m
^Limitations of dimensions
^Limitations of dimensions
- Dimensional analysis does not give any information about the scalar or vector nature of the quantity.
- Dimensions for
v = u + at etc. can’t be calculated in exact form. - Dimensional formulae of the quantities depending on more than three variables cannot be obtained.
- Dimensional formulae of the quantities involving trigonometric logarithmic or exponential functions cannot be calculated.
- Value of proportionality constant can’t be calculated.
It doesn’t distinguish between the physical quantities having same dimensions.
*Dimensional Constants
*Dimensional Constants
All constants are not dimensionless. The physical quantities which have constant values and dimensions as well are called dimensional constants.
e.g. Planck’s constant, Boltzmann’s constant & Gravitational constant etc.
*Some SI Derived units with special names
*Some SI Derived units with special names
| Quantity | SI unit | Symbol |
| Force | newton | N |
| Work | joule | J |
| Pressure, Stress | pascal | Pa |
| watt | W | |
| Angle | radian | rad |
| Frequency | hertz | Hz |
| Viscosity | poiseuille | Pl |
| Torque | newton meter | Nm |
| Electric charge | coulomb | C |
| Electrical resistance | ohm | W |
| Voltage | volt | V |
| Flux (Elec. or mag) | weber | Wb |
| Inductance | henry | H |
| Capacitance | farad | F |
| Magnetic field | tesla | T |
| Illuminance | lux | Lx |
| Luminous flux | Lumen | lm |
| Illuminance | lux | lx |
| Activity (radioactive) | Becquerel | Bq |
| Absorbed dose index | Gray | Gy |
*Average value of a quantity
*Average value of a quantity
If a quantity y varies with x, then its average value in the interval x e [a, b] is defined as,
Average value for one complete cycle
- of sinθ & cosθ is zero.
- of sin2 θ & cos2θ is half.
*Inverse function
*Inverse function
Function of the form, 
have the shown variation. All the curves pass through the point (1, 1). For n > 1 the graph lies above the rectangular hyperbola
(n =1) in the region
0 < x < 1 and then lies below it in the region x > 1. For 0 < n < 1 the graph first lies below the hyperbola in the region 0 < x < 1 and then lies above the hyperbola in the region x > 1.
*Vertical line
*Vertical line
Function x = a represents a vertical line located right side of y axis if a = +ve & left side of y axis if a = – ve.
