# Chapter 10 Motion and Measurement of Distances

• Movement of object or any living thing from one place to another with the help of transport is known as transportation.
• There are different mode of transport like bus, bicycle, aero-plane, ship, bullock cart etc.
• A known quantity which is fixed us called as unit.
• In earlier times, we use foot length, hand span for the measurement.
• In 1790, standard unit of measurement is created by French, called metric system and it is followed all over the world.
• We can measure correctly with the help of a scale.
• A change in the position of the object or anything called motion. Example: moving bicycle etc.
• Motion are of different types: Rotatory motion, Oscillatory motion, rectilinear motion, Circular motion etc.
• Meter is the SI unit of length.

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### Exercise 1 ( Page No. : 106 )

•  Q1 Give two examples each, of modes of transport used on land, water and air. Ans: Transportation is the method through which one object can move from one place to another through the transport. There are different modes of transport system on the basis of their requirement. Land transport: All automobiles like car, buses, trucks, bicycle are the examples of land transport.  Water transport: Ship, boat, water crafts are the examples of water transport. Air transport: Aero-plane, helicopter, gliders are the examples of air transport. Q2 Fill in the blanks: (i) One metre is ______________ cm. (ii) Five kilometre is ______________ m. (iii)Motion of a child on a swing is ______________. (iv)Motion of the needle of a sewing machine is ______________. (v) Motion of wheel of a bicycle is______________. Ans: (i) 100                                                                                                                                                                                                                                                 According to metric scale, 1 meter = 100 cm. (ii) 5000                                                                                                                                                                                                                                                                  1 km = 1000 meter 5 km = 5 x 1000 = 5000 meter (iii) Circular                                                                                                                                                                                                                              Motion that occurs in circle is known as circular motion. (iv) Periodic motion                                                                                                                                                                                                                Motion that occurs after the same interval of time is known as periodic motion. (v) Circular motion                                                                                                                                                                                                                 Motion that occurs in a circular path or when a body moves round and round called as it have circular motion. Q3 Why can a pace or a footstep not be used as a standard unit of length? Ans: A pace or a footstep not be used as a standard unit of length because its size of the foot can be increase with the time. Footsteps size is differ from person to person. So, it cannot be used as a standard unit of length. Q4 Arrange the following lengths in their increasing magnitude: 1 metre, 1 centimetre, 1 kilometre,1 millimetre. Ans: 1 mili-meter = 0.001 meter 1 kilometer = 1000 meter 1 centimeter = 0.01 meter So, 1 mm < 1 cm. < 1 m. < 1 km Q5 The height of a person is 1.65 m. Express it into cm and mm. Ans: Height of the person is 1.65 meter. 1m. = 100 cm.                                                                                                                                                                                                               1.65  = 1.65 x 100                                                                                                                                                                                                                          100             1.65 m. = 165 cm. 1 m. = 1000 mili- meter            1.65 m = 165 x 1000 = 1650 mm                                                                                                                                                                                                                     100 Q6 The distance between Radha's home and her school is 3250 m. Express this distance into km. Ans: Distance between Radha’s home and her school is 3250 meter. 1 m = 0.001 km 3250 m = 3250 x   1     .                                                                                                                                                                                                                                                      1000 3250 m = 3.25 km. Q7 While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm and at the other end is 33.1 cm. What is the length of the needle? Ans: Reading of the scale at one end = 3.0 cm Reading of the scale at other end = 33.1 cm Total length of the needle = 33.1 – 3.0                                          = 30.1 cm. Q8 Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on. Ans: Similarities between motion of bicycle and a ceiling fan: Bicycle and ceiling fan both show circular motion. They both are fixed as wheel of bicycle is fixed as the ceiling fan. Differences: Both shows different motion when fan is switched on. Like bicycle shows rectilinear motion but ceiling fan shows the circular motion. When a bicycle wheel rotates, movement from one place to another place occurs, whereas fan is fixed. Q9 Why could you not use an elastic measuring tape to measure distance? What would be some of the problems you would meet in telling someone about a distance you measured with an elastic tape? Ans: We could not use elastic tape to measure distance because due to elasticity its measurement is not accurate or we can say not approximate. An elastic tape is stretched when we hold it from one end. Sometimes its size is reversed. So, accurate measurement is not taken by an elastic tape. Q10 Give two examples of periodic motion. Ans: A motion which occurs in a definite interval of times is called periodic motion. For example: needle of a sewing machine, a child on swing, needle of a clock etc.