Science STD 6 Chapter 7: Motion and Measurement of Distances - Exercises
1. Give two examples each, of modes of transport used on land, water and air.
Examples of modes of transport are:
- Land: cars, buses
- Water: boats, ships
- Air: aeroplanes, helicopters
2. Fill in the blanks:
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One metre is ............. cm.
100
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Five kilometre is ............. m.
5000
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Motion of a child on a swing is .............
periodic motion
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Motion of the needle of a sewing machine is .............
periodic motion
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Motion of wheel of a bicycle is .............
circular motion
3. Why can a pace or a footstep not be used as a standard unit of length?
A pace or a footstep cannot be used as a standard unit of length because the length of a person's foot or step varies from person to person. This would cause confusion and inconsistent measurements, as the same distance would be measured as a different number of footsteps by different people.
4. Arrange the following lengths in their increasing magnitude: 1 metre, 1 centimetre, 1 kilometre, 1 millimetre.
The lengths in increasing order are: 1 millimetre, 1 centimetre, 1 metre, 1 kilometre.
5. The height of a person is 1.65 m. Express it into cm and mm.
The height of a person in cm and mm is:
- Height in cm: 1.65 m × 100 cm/m = 165 cm
- Height in mm: 165 cm × 10 mm/cm = 1650 mm
6. The distance between Radha's home and her school is 3250 m. Express this distance into km.
To convert metres to kilometres, divide by 1000.
Distance in km = 3250 m / 1000 = 3.250 km.
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?
The length of the needle is calculated by subtracting the initial reading from the final reading.
Length = 33.1 cm - 3.0 cm = 30.1 cm.
8. Write the similarities and differences between the motion of a bicycle and a ceiling fan that has been switched on.
Similarities: The wheels of a bicycle and the blades of a ceiling fan both undergo circular motion.
Differences: A bicycle, as a whole, moves from one place to another (rectilinear motion), whereas a ceiling fan remains in a fixed position (at rest).
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?
An elastic measuring tape should not be used because its length changes when stretched, leading to inconsistent and inaccurate measurements. A major problem is that the person you are telling the measurement to would not know how much the tape was stretched, making the measurement unreliable and incomparable.
10. Give two examples of periodic motion.
Two examples of periodic motion are:
- A child swinging on a swing.
- The motion of a pendulum.
Suggested Projects and Activities
1. Draw a map of your classroom. Roll a ball on the floor. In your map mark the points where the ball started and where it stopped. Show also the path it moved along. Did the ball move along a straight line?
Outline: This activity demonstrates the concept of rectilinear motion. Students will draw a map and then trace the path of a ball. The answer will likely show that the ball's path is not perfectly straight due to friction and other factors. This helps students understand that ideal rectilinear motion is rare in everyday life and that real-world motion often combines different types of movement.
2. Using string and a scale, let each student measure the length of his/her foot. Prepare a bar graph of the foot length measurements that have been obtained for the whole class.
Outline: This activity reinforces the need for standard units of measurement. Students will measure their foot length using a non-standard unit (string) and then a standard unit (scale). By creating a bar graph of the data, they will visually see the variation in foot length among their peers, proving that a foot's length is not a reliable standard unit.