Motion and Measurement of Distances

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Question 18

How are the motions of a wheel of a moving bicycle and a mark on the blade of a moving electric fan different? Explain.

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Question 17

While travelling in a train, it appears that the trees near the track are moving whereas co-passengers appear to be stationary. Explain the reason.

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Question 9

You are provided three scales A, B and C as shown in Fig. to measure a length of 10 cm.

For the correct measurement of the length, you will use the scale,

(a) A only

(b) B only

(c) C only

(d) Any of three scales

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Question 5

Paheli moves on a straight road from point A to point C. She takes 20 minutes to cover a certain distance AB and 30 minutes to cover the rest of distance BC. She then turns back and takes 30 minutes to cover the distance CB and 20 minutes to cover the rest of the distance to her starting point. She makes 5 rounds on the road the same way. Paheli concludes that her motion is

(a) Only rectilinear motion.

(b) Only periodic motion.

(c) Rectilinear and periodic both.

(d) Neither rectilinear nor periodic.

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Question 13

The photograph given above shows a section of a grille made up of straight and curved iron bars. How would you measure the length of the bars of this section, so that the payment could be made to the contractor?

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Question 15

Four children measure the length of a table which was about 2 m. Each of them used different ways to measure it.

(i) Sam measured it with a half metre long thread.
(ii) Gurmeet measured it with a 15 cm scale from her geometry box.
(iii) Reena measured it using her hand span.
(iv) Salim measured it using a 5 m long measuring tape.

Which one of them would get the most accurate length? Give reason for your answer.

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Question 19

Three students measured the length of a corridor and reported their measurements. The values of their measurements were different. What could be the reason for the difference in their measurements?

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Question 12

Write one example for each of the following type of motion.

(i) Rectilinear
(ii) Circular
(iv) Periodic
(v) Circular and periodic

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Question 10

Correct the following.
i) The motion of a swing is an example of rectilinear motion.
ii) 1m = 1000 cm

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Question 7

Four pieces of wooden sticks A, B, C and D are placed along the length of 30 cm long scale as shown in Fig. Which one of them is 3.4 cm in length?