Motion and Measurement of distances
1.What do you mean by rest and motion?
Ans A body is said to be at rest when it doesn't change its position with respect to its surrounding object.
eg a rope lying on the floor. A body is said to be at motion when it changes its position with respect to its surrounding. eg a moving car.
2. What is the need of measurement. What are standard units and why are they important?
Ans It is difficult to make correct judgement without making actual measurement. Therefore to make your judgement more reliable and accurate actual measurements are taken.
The unit which is acceptable to the majority of the people as a basic unit of measurement is called a standard unit for the people.
For uniformity and convenience a common unit is necessary for a measurement of a physical quantity.
3. What is measurement and unit?
Ans Measurement is the comparison of an unknown quantity with a known fixed quantity of the same kind.
The known fixed quantity is called unit.
4. What do you mean by International System of units (SI)?
Ans Scientists all over the world have accepted a basic set of units for the measurement of physical quantity(SI).
According to the system of SI unit of length is metre (m) mass in kilogram (kg) time is seconds (s) and temperature is Kelvin (K).
The distance between the tip of the middle finger and elbow is Cubit.
The distance between the tip of the thump and little finger is Hand span.
Distance between the feet is called Pace.
Ans A body is said to be at rest when it doesn't change its position with respect to its surrounding object.
eg a rope lying on the floor. A body is said to be at motion when it changes its position with respect to its surrounding. eg a moving car.
2. What is the need of measurement. What are standard units and why are they important?
Ans It is difficult to make correct judgement without making actual measurement. Therefore to make your judgement more reliable and accurate actual measurements are taken.
The unit which is acceptable to the majority of the people as a basic unit of measurement is called a standard unit for the people.
For uniformity and convenience a common unit is necessary for a measurement of a physical quantity.
3. What is measurement and unit?
Ans Measurement is the comparison of an unknown quantity with a known fixed quantity of the same kind.
The known fixed quantity is called unit.
4. What do you mean by International System of units (SI)?
Ans Scientists all over the world have accepted a basic set of units for the measurement of physical quantity(SI).
According to the system of SI unit of length is metre (m) mass in kilogram (kg) time is seconds (s) and temperature is Kelvin (K).
The distance between the tip of the middle finger and elbow is Cubit.
The distance between the tip of the thump and little finger is Hand span.
Distance between the feet is called Pace.
The commonly used units of length are- cm, m, mm, km, etc.
5. Raju and Kevin live 2000 m away from each other. Express the distance between them in km.
Ans 2000 m = 2km
length is measured by a ruler, measuring rod, etc.
odometer is a device used to measure distance covered by a vehicle.
mass is a quantity of matter contained in an object. It is measured in kg in SI units.
The devices used to measure mass are spring balance, beam balance, electronic balance, etc.
Time is measured in sec in SI units using clock, wrist watch, etc.
Temperature is measure of coldness or hotness.
It is measured by thermometer.
6. List the precautions that one should take while measuring length with a ruler.
Ans We should take the following precautions while measuring length with a ruler -
1. Care should be taken to keep the ruler along the objects.
2. Eye should be exactly above the pint where the measurement has to be taken.
3. If the edge of the ruler is worn out or broken the measurement should be taken from any other mark, that is fully clear and then subtract the final measurement by that number.
7. How can we measure the diameter of a ball or a coin?
Ans To measure the diameter of a ball or coin we should use two wooden blocks. Place the ball or coin on a table and place the blocks such that both the blocks touch the ball. Now keep a ruler near the lower edges of the wooden blocks. Now measure the distance between the faces touching the ball. This is the diameter.
8. Write the different types of motion?
Ans 1. Translatory motion- When all parts of an object move the same distance at the same time. then the object is said to be in translatory motion.
It is of two kinds-
a) Rectilinear motion- When all the parts of an object cover the same distance along a straight line in a given time. It is said to be in rectilinear motion.
eg a train moving in a straight track, etc
b) Curvilinear motion- When an object moves around a curve line is called curvilinear motion.
eg a car moving in a curve road, etc.
2. Circular motion- When an object moves in a circular path around a fixed path and point it is said to be in circular motion.
It is of two types-
a) Rotational- When a body moves about a fixed axis without changing its motion It is said to be at rotational motion.
eg blades of a moving fan, etc.
b) Revolution- When the objects change its position when it moves in a circular path is said to be at revolution.
eg revolution of Earth
3.Periodic motion- The motion which repeats itself after some interval of time is called periodic motion.
eg heartbeat, pendulum of a clock, etc.
4. Non-Periodic motion- A motion that doesn't repeat itself in an interval of time is called non-periodic motion.
eg movement of a child, ducks waddling in water, etc.
5. Oscillatory motion- When a body moves to and fro about its mean position is called an oscillatory motion. eg pendulum of a clock, strings of a guitar.
6. Simultaneous motion- When an object undergo a combination of different types of motion then the body is said to be at simultaneous motion.
eg motion of Earth, wheels of a cycle, a ball rolling in a straight way.
9. What are the disadvantages of conventional methods of measurement?
Ans In conventional methods of measurement we use different body parts (cubit, hand span, etc) They are not reliable as they don't give accurate measurement as it varies from person to person.
Temperature is measure of coldness or hotness.
It is measured by thermometer.
6. List the precautions that one should take while measuring length with a ruler.
Ans We should take the following precautions while measuring length with a ruler -
1. Care should be taken to keep the ruler along the objects.
2. Eye should be exactly above the pint where the measurement has to be taken.
3. If the edge of the ruler is worn out or broken the measurement should be taken from any other mark, that is fully clear and then subtract the final measurement by that number.
7. How can we measure the diameter of a ball or a coin?
Ans To measure the diameter of a ball or coin we should use two wooden blocks. Place the ball or coin on a table and place the blocks such that both the blocks touch the ball. Now keep a ruler near the lower edges of the wooden blocks. Now measure the distance between the faces touching the ball. This is the diameter.
8. Write the different types of motion?
Ans 1. Translatory motion- When all parts of an object move the same distance at the same time. then the object is said to be in translatory motion.
It is of two kinds-
a) Rectilinear motion- When all the parts of an object cover the same distance along a straight line in a given time. It is said to be in rectilinear motion.
eg a train moving in a straight track, etc
b) Curvilinear motion- When an object moves around a curve line is called curvilinear motion.
eg a car moving in a curve road, etc.
2. Circular motion- When an object moves in a circular path around a fixed path and point it is said to be in circular motion.
It is of two types-
a) Rotational- When a body moves about a fixed axis without changing its motion It is said to be at rotational motion.
eg blades of a moving fan, etc.
b) Revolution- When the objects change its position when it moves in a circular path is said to be at revolution.
eg revolution of Earth
3.Periodic motion- The motion which repeats itself after some interval of time is called periodic motion.
eg heartbeat, pendulum of a clock, etc.
4. Non-Periodic motion- A motion that doesn't repeat itself in an interval of time is called non-periodic motion.
eg movement of a child, ducks waddling in water, etc.
5. Oscillatory motion- When a body moves to and fro about its mean position is called an oscillatory motion. eg pendulum of a clock, strings of a guitar.
6. Simultaneous motion- When an object undergo a combination of different types of motion then the body is said to be at simultaneous motion.
eg motion of Earth, wheels of a cycle, a ball rolling in a straight way.
9. What are the disadvantages of conventional methods of measurement?
Ans In conventional methods of measurement we use different body parts (cubit, hand span, etc) They are not reliable as they don't give accurate measurement as it varies from person to person.
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