Motion and Measurement of DistancesNCERT Solution and other Questions and Answers
Q1: Give two examples each, of modes of transport used on land, water and air.
- On Land: Bicycle, Car, Bus
- On Water: Ship, Boat, Ferry
- On Air: Helicopter, Aeroplane, Glider
Q2: Fill in the blanks:
(i) One metre is ____100_ cm.
(ii) Five kilometre is ___5000_ m. (1 Km = 1000m)
(iii) A motion of a child on a swing is ___periodic motion__.
(iv) A motion of the needle of a sewing machine is __periodic motion_.
(v) A motion of a wheel of a bicycle is__circular motion_.
Q3: Why can a pace or a footstep not be used as a standard unit of length?
Answer: A pace or a footstep not be used as a standard unit of length because the size of pace and footstep vary from person to person. This will lead to confusion while measuring the lengths by different persons. We should use standard units like International System of Units (SI Units).
Q4: 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
Q5: The height of a person is 1.65 m. Express it into cm and mm.
Answer: 1m = 100cm and 1cm = 10mm
∴ 1.65 m = 1.65 x 100cm = 165cm
Also, 1.65m = 165cm = 165 x 10mm = 1650 mm
Q6: The distance between Radha's home and her school is 3250 m. Express this distance into km.
Answer: Since 1 m = 1 ÷ 1000km
∴ 3250m = 3250 ÷ 1000 = 3.250 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?
Answer: Length of the needle = Final reading - Starting Reading
= 33.1 cm - 3.0 cm = 30.1 cm
Q8: Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Answer: Similarity: Both ceiling fan and bicycle exhibit circular motion.
Difference: Bicycle shows rectilinear motion while ceiling fan does not.
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?
Answer: Since the tape is stretchable, its measurements will be inaccurate. Therefore we cannot use it as measuring tape. While measuring a distance, we need to tell someone how much tape has been stretched which is difficult to measure. It leads to incorrect measurements.
Q10: Give two examples of periodic motion.
Answer: Pendulum, Guitar String, Needle of Sewing Machine.
Q11: Which invention lead to a great change in modes of transport?
Answer: Invention of Wheel
Q12: Before 19th century which power was used in transportation?
Answer: Till the beginning of 19th century, people rely on animal power to transport them from one place to another.
Q13: Which invention as a new source of power led to the development of railroads?
Answer: Steam engine.
Q14: Name the 20th-century inventions in the field of transportation.
Answer: Electric train, monorail, supersonic aeroplanes and spacecraft.