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Measurement And Motion
What is translatory motion
If a body moves as a whole such that every part of the body moves through the same distance in a given time the body is in translatory motion.If the body moves in a straight line its motion is said to be rectilinear.A car moving along a straight road is in rectilinear motion.If it moves along a curved line the motion is said to be curvilinear.When a car or a ship turns it moves along a curved path and is in curvilinear motion.
What is the difference between circular and oscillary motion
The motion of a body in circular path around a fixed point or a fixed axis is known as circular motion.When a body moves to and fro about a fixed point it is said to be in oscillatory motion or vibratory motion.The oscilation of a pendulum and the vibration of a stretched wire.
Differentiate between revolution and rotation.
If a body or a whole moves around in a circular path, the motion is known as revolution.The motion of the moon around the earth or the earth around the sun.If the body turns without shifting its position from one place to another its motion is called rotation.The rotation of the blade of a fan and a spinning top.
Why is it essential to have a standard system of unit
Various countries devised and used their own system of units.So there were many such units this was very confusing.A man who weighed 72 kg in France weighed 158.4 lb in England.The length of a foot or hand differs from person to person and therefore this cannot be used as reliable unit of measurement.For accurate measurement we need some standard representation of every physical quantity.So it is essential to have a standard system of units that has same definite and convenient quantity in it so that it remains the same whenever and by whoever it is used.
How can you measure the length of a curved line
To measure the length of a curved line using a divider
Open out the divider so that the legs are about 5 mm apart.
Place one of the legs at one end of the line and the other leg on the line.
Without altering the distance between the legs of the divider take the divider along the line .
Count the number of steps taken to cover the entire length of the line.
If some portion less than the distance between the two legs is left out measure it separately by adjusting the distance between the legs.
The length of the line is obtained as
The length of the line is obtained as length
Number of steps X distance between the legs + the left over length.