6 Science Chapter 10 Motion And Measurement Of Distances

Chapter Notes and Summary
• There are various modes of transport that are used to go from one place to another.
(i) Land transport
(ii) Water transport
(ii) Air Transport
• actual path length covered by an object between two points is called distance.
• comparison of an unknown quantity with some known quantity is known as measurement.
• unit of measurement is known fixed quantity which is used as a standard for measurement of physical quantity.
SI units : standard system of unit is called SI system (System International and ‘Unites’ in french). SI units for measuring length, mass and time are metre (m), kilogram (kg) and second (s), respectively.
1 m = 100 cm 1 cm = 10 mm
• For measuring large distances, metre is not a convenient unit. Its larger unit is kilometre (km).
1 km = 1000 m
• SI units are based on MKS (metre for length, kilogram for mass, second for time) system of units.
Advantages of SI system :
• Universally accepted standardised set of units.
• Even very small measurements are possible in their system.
• units do not change with time.
• An object that changes its position with time, relative to its surroundings, is said to be in motion.
• An object that does not change its place or position with time, relative to its surroundings is said to be stationary or at rest.
• Motion can be divided in to following types-translational, circular, rotational, oscillatory and random
• When an object moves in same direction and cover equal distance in a given interval of time, then such motion is called translational motion.
• When a body moves along a straight line then it is called linear or rectilinear motion.
• When an object moves along a circular path, it is said to be in circular motion.
• When an object moves about its axis, it is called rotational motion.
• When an object moves to and fro about a fixed point, it possesses periodic motion.
• rate of movement of an object is determined by measuring distance travelled with time.
• One complete cycle from point of release to other extreme and back to initial point is called one oscillation.
• A very fast back and forth motion is called vibratory motion.
• When a body moves in different directions and does not have a fixed path, it is called random motion.

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