Key words (Motion and Measurement)
1. Circular Motion: Circular motion is a movement of an object along a circular path. Eg. Blades of a Fan, and Hands of a clock execute Circular Motion.
2. Distance: The total path covered by a body which is under motion is called distance. The Path covered to travel from Dalhousie to Banikhet is 6 kilometer , hence distance between Banikhet and Dalhousie is 6 Km.
3. Measurement: To find the length, breadth, or other dimensions of a body is called measurement.
4. Motion: If a body changes its position or location with respect to time and position, then it is said to be in motion.
5. Periodic Motion: The type of motion which returns itself after a fixed time interval is called Periodic motion. Eg.- Movement of Earth around Sun.
6. Rectilinear Motion: It is the motion of a body which moves in a straight line or path.
7. SI Units: International system of units which is accepted and recognized world wide.
8. Units of Measurement: The standards for measurement of Physical quantities are called Units of measurement. Eg. Meter is the unit of length and Kg is the unit of mass.
NCERT Exercise Questions:
1. Give two examples each , of modes of transport used on land, water and air.
Answer-
Means of transport used on Land : Bus, Truck
Means of transport used on Water: Boat, Ship
Means of transport used on air: Airplane, Helicopter.
2. Fill in the Blanks:
a) One meter is 100 cm.
b) Five Kilometer is 5000 m.
c) Motion of a child on a swing is Periodic motion.
d) Motion of the needle of a sewing machine is Periodic motion.
e) Motion of wheel of a bicycle is Circular and rectilinear.
3. Why can a pace or a footstep not be used as a standard unit of length?
Answer- A Pace or a footstep cannot be used as a standard unit of length because these things differe for different persons and aren’t equal for all.
4. Arrange the following lengths in their increasing magnitude:
1 meter, 1 centimeter, 1 Kilometer, 1 millimeter
Answer: 1 millimeter < 1 centimeter < 1 meter < 1 Kilometer.
5. The height of a person is 1.65 m. Express it into cm and mm.
Answer– 1.65m = 1.65 X100 = 165 cm
1.65m = 1.65 X 1000 = 1650 mm
6. The Distance between Radha’s home and her school is 3250 m. Express this distance into km.
Answer- Distance between Radha’s home and school = 3250 m= 3250/1000 km= 3.250 km
3.250 km = 3 km 250 m.
7. While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and the other end is 33.1 cm. What is the length of the needle?
Answer: Length of the needle= difference between readings at two ends of the scale
= 33.1- 3.0 = 30.1 cm
8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Answer:
Similarities: The wheels of the bicycle and the blades of the fan both execute circular motion.
Differences: The wheels of the bicycle also execute rectilinear motion, but the blades of fan do not leave the place and execute only circular motion.
9. Why would you not like to use a measuring tape made of an elastic material like rubber to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with such a tape?
Answer: We would not like to use a measuring tape made of an elastic material to measure distance because The measuring tape made of elastic material will have different lengths in different cases and will not have a definite fixed length. We will get different measurements for similar lengths.
10. Give two examples of periodic motion.
Answer: Earth rotating about its own axis.
Revolution of Earth around Sun.
