Textbook Questions
Q1. Give two examples of each of the modes of transport used on land, water and air.
Ans: Two modes of transport used on
| Land | Bus and train |
| Water | Ship and boat |
| Air | Aeroplane and helicopter |
Q2. Fill in the blanks.
- One meter is 100 cm
- Five kilometres is 5000m.
- The motion of a child on a swing is periodic motion.
- The motion of the needle of a sewing machine is a Periodic motion
- The 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 cannot be used as a standard unit of length because the pace or footstep of every person is not the same.
Q4. Arrange the following lengths in their increasing magnitude.
1 metre, 1 centimetre, 1 kilometre, 1 millimetre.
Ans: 1mm< 1cm< 1m< 1km.
Q5. The height of a person is 1.65m. Express it into cm and mm.
Ans:
Given,
Height of the person = 1.65m
We know that, 1m = 100cm
Then,
1.65m = (1.65 x 100)cm = 165 cm
∴ The height of the person is 165cm
Again,
Height of the person in mm =?
We know that 1m = 1000 mm
so, 1.65m = (1.65 x 1000)mm = 1650 mm.
∴ The height of the person is 1650mm.
Q6. The distance between Radha’s home and her school is 3250 m. Express this distance into Km.
Ans:
The distance between Radha’s home and her school = 3250m
We know that 1km = 1000m
i,e, 1m = 1/1000 km
So, 3250 m = 3250/1000 km = 3.25 km.
∴ The distance from Radha’s home and her school is 3.25 km.
Q7. While measuring the length of a knitting needle. The scale reading at one end is 3.0cm and at the other end is 33.1 cm. What is the length of the needle?
Ans: The length of the needle = 33.1cm – 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:
Similarities:
- The blades of a fan and the wheels of a bicycle are fixed at a point.
- Both have a circular motion about their respective fixed points.
Differences:
- A bicycle has a rectilinear motion whereas the blades of a ceiling fan have circular motion.
Q9. 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?
Ans: An elastic measuring tape is stretchable. So, the length of the tape may change on stretching. As a result, the measured length would not be correct.
Some of the problems are:
- The length of the elastic tape varies and depends upon the force by which it is stretched.
- Measurement may also vary if different persons measure the same distance.
Q10. Give two examples of periodic motion.
Ans: The two examples of periodic motion are:
1. Motion of a pendulum.
2. Motion of a boy sitting on a swing.
Extra Questions and Answers
Q1. Name some units of measurement used in ancient times.
Ans: Length of a foot, width of a finger and the distance of a step.
Q2. What is the SI unit of length?
Ans: Metre.
Q3. Define measurement.
Ans: Measurement can be defined as the technique or process for correctly judging the dimensions of various objects.
Q4. What is motion?
Ans: Motion is the change in position of an object with respect to its surroundings in a given interval of time.
Q5. What is rest?
Ans: If a body does not change its position with respect to its surroundings, the body is said to be in rest.
Q6. What are circular motion and periodic motion?
Ans: Circular Motion: The motion of an object in a circular path is called a circular motion.
Periodic Motion: The motion of an object that repeats itself after regular intervals of time is called a periodic motion.
