Q1. Give two examples each, of modes of transport used on land, water and air.
Land transport: Bus, train, motorbike.
Water transport: Boat, Ship, steamer.
Air Transport: Aeroplane, Helicopter.
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______________.
(i) One metre is 100 cm.
(ii) Five kilometre is 5000 m.
(iii) Motion of a child on a swing is periodic motion.
(iv) Motion of the needle of a sewing machine is periodic motion.
(v) Motion of the wheel of a bicycle is 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 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 the International System of Units (SI Units).
Q4. Arrange the following lengths in their increasing magnitude: 1 metre, 1 centimetre, 1 kilometre, 1 millimetre.
Ans: 1 millimetre, 1 centimetre, 1 metre, 1 kilometre.
Q5. The height of a person is 1.65 m. Express it into cm and mm.
Ans: We know that 1 metre = 100 cm and 1 metre = 1000 mm So, 1.65 m = 1.65 × 100 = 165 cm and 1.65 m = 1.65 × 1000 = 1650 mm
Q6. The distance between Radha's home and her school is 3250 m. Express this distance into km.
Ans: We know that 1 m = 1/1000 km So, 3250 m = 3250/1000 km = 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: The length of the needle = 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.
Ans: Similarity: Both show a circular motion.
Difference: Bicycle shows a rectilinear motion whereas a 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?
Ans: Since the tape is stretchable, it will show the same measurements for different lengths. 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.
Ans: Rotation of Earth, Pendulum, vibrating wire of the guitar, etc.