Motion and Measurement of Distances
Chapter 10
Exercises (অনুশীলনী)
- Give two examples each, of modes of transport used on land, water and air.
Ans:- Soil- buses and trains.
Water- boats and ships.
Air- aircraft and helicopters.
- Fill in the blanks:
(i) One metre is _ cm.
Ans:- 100.
(ii) Five kilometre is __ m.
Ans:- 5000.
(iii) Motion of a child on a swing is __ .
Ans:- Periodic motion.
(iv) Motion of the needle of a sewing machine is _ .
Ans:- Periodic motion.
(v) Motion of wheel of a bicycle is _ .
Ans:- Circular motion.
- Why can a pace or a footstep not be used as a standard unit of length?
Ans:- Because every person’s foot measurements or footprints Not equal.
- 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.
- The height of a person is 1.65 m. Express it into cm and mm.
Ans:- I know that,
1 m = 100 cm:
So 1.65 m = 1.65 x 100 cm.
= 165 cm:
Again,
1 cm = 10 mm
So,
1.65 m = 165 cm = 165 x 10 mm
= 1650 mm:
- The distance between Radha’s home and her school is 3250 m. Express this distance into km.
Ans:- I know that,
1 km = 1000 m
So 3250 / 1000 = 3.250 km
- While measuring the length of a knitting needle, the reading of the scale at one end is 3.0 cm nd at the other end is 33.1 cm. What is the length of the needle?
Ans:- it is given ,
One end of the scale, which measures the length of the shell, has a value of 3.0 cm.
And the value of the other end is 33.1 cm.
So the length of the shell will be = 33.1 cm – 3.0 cm.
= 30.1 cm: - Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Ans:-
Similarity- The running ceilingfan and the bicycle are moving.
The contrast -The wheel of the bicycle is moving linearly but the ceilingphen does not move linearly.
- Why would 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:- The reason why we cannot use elastic measurements to measure the elasticity is because-
- The size of different people measuring the same distance will be different.
2) Using the size of the elastic changes in the length of the measure depending on the force to be applied.
- Give two example of periodic motion.
Ans:- 1) The clock swing.
2) Injection of sewing machine.