Chapter 10 Motion and Measurement of Distances
Question 1: Give two examples each, of modes of transport used on land, water and air.Answer:
Land - Car, Bus
Water - Ship, Boat
Air - Plane, Helicopter
Question 2: 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______________.
Answer:
i) One metre is 100 cm.
ii) Five kilometre is 5000 m.
iii) Motion of a child on a swing is periodic.
iv) Motion of the needle of a sewing machine is periodic.
v) Motion of the wheel of a bicycle is circular.
Question 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 as it varies from person to person. And therefore, the standard unit of length is meter which is 100 cm.
Question 4: Arrange the following lengths in their increasing magnitude:
1 metre, 1 centimetre, 1 kilometre, 1 millimetre.
Answer:
1 millimetre, 1 centimetre, 1 metre, 1 kilometre
Question 5: The height of a person is 1.65 m. Express it into cm and mm.
Answer:
Height of a person (in meter) = 1.65 m
Height of person (in centimetre) = ?
= 1 m = 100 cm
= 1.65 m = 1.65 × 100
= 1.65 m = 165 cm
Height of person (in meter) = 1.65 m
Height of person (in millimetre) = ?
= 1 m = 1000 mm
= 1.65 m = 1.65 × 1000
= 1.65 m = 1650 mm
Question 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 her school (in meter) = 3250 m
Distance between Radha’s home and her school (in kilometre) = ?
Let the distance between Radha’s home and her school (in kilometer) be x.
= 1 km = 1000 m
= x = 3250 m
= x = 3250/1000
= x = 3.25 km
Therefore, the distance between Radha’s home and her school is 3.25 m.
Question 7: 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?
Answer:
Length of the reading of the scale at one end = 3.0 cm
Length of the reading of the scale at another end = 33.1 cm
Length of needle = ?
= Length of needle = Length of the reading of the scale at another end - Length of the reading of the scale at one end
= Length of needle = 33.1 cm - 3.0 cm
= Length of needle = 30.1 cm
Therefore, the length of the knitting needle is 30.1 cm.
Question 8: Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Answer:
→ Similarities - The blades of a fan and the wheels of a bicycle shows circular motion
→ Differences - Bicycle move in rectilinear motion, but the fan does not move in rectilinear motion.
Question 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: Elastic tapes are stretchable. So, the length of an elastic measuring tape will change each time due to stretching. So, it will not give correct measurement of a distance. Therefore, we cannot use an elastic measuring tape to measure distance.
Question 10: Give two examples of periodic motion.
Answer:
→ Motion of a child on a swing is periodic.
→ Motion of the needle of a sewing machine is periodic.
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