NCERT Exemplar Solutions Class 6 Science Motion and Measurement of Distances

The length of the ribbon is between
(a) 1.15 m-1.25 m
(b) 1.25 m-1.35 m
(c) 1.50 m-1.60 m
(d) 1.60 m-1.70 m

Solution 4:  The right thing for which selection is made is (b) 1.25 m-1.35 m. 

 Since the ribbon is folded five times, i.e. from the figure,

 ribbon length = (27.5-2) cm x 5 = (25.5 x 5) cm

= 127.5 cm = 1.27 m [almost 1m = 100 cm]

Question 5:   Paheli moves on a straight road from point A to point C. She takes 20 min to cover a certain distance AB and 30 min to cover the rest of distance BC. She then turns back and takes 30 min to cover the distance CB and 20 min to cover the rest of the distance to her starting point. She makes 5 rounds on the road in the same way. Paheli concludes that her motion is:
(a) only rectilinear motion
(b) only periodic motion
(c) rectilinear and periodic motion
(d) neither rectilinear nor periodic

Solution 5:  The right thing for which selection is made is (c) rectilinear and periodic motion.

Therefore, we can see that Paheli moves from A -> C and from C -> A on a straight line. So, the motion is rectilinear, since she makes 5 rounds in the same way and crosses point 6 in each round, after a normal time interval, Paheli moves in a periodic motion. So, her motion is periodic and rectilinear.

As compared to Golu, Bholu covers a
(a) longer distance but with a lower speed
(b) longer distance with a higher speed
(c) shorter distance with a lower speed
(d) shorter distance with a higher speed
which is longer than that of Golu. 

Solution 6:   The right thing for which selection is made is (b) longer distance with a higher speed. 

It is obvious from the figure that, at the same time, both hit point B, so Bholu would have to travel faster to cover more distance and Golu is on the track with the shortest distance between A and B. Thus, Bholu travels at a greater velocity than Golu.

Solution 7:  The right thing for which selection is made is (c) C. 

 It is clear, from the figure that,
length of A = (2.7 – 0.3) cm = 2.4 cm,
length of S = (6.5 – 3.4) cm = 3.1 cm
length of C = (10.4 – 7.0) cm = 3.4 cm and
length of D = (14.4 – 10.7) cm = 3.7 cm
so, length of C is same as 3.4 cm that will asked.

Question 8:  Which of the following figure shows the correct placement of a block along a scale for measuring its length?

Solution 8:  The right thing for which selection is made is (c).

We can see that in above options, (a), (b) and (d) have block positioning that comes out of the 15 cm scale marking. Only (c) has the position within the scale label.

Question 9:  You are provided three scales A, B and C as shown in figure to measure a length of 10 cm.

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

(a) only A
(b) only B
(c) only C
(d) Any of the three scales

Solution 9:  The right thing for which selection is made is (d) any of the three scales. 

We can see that on their non-broken sides, all the scales have a 10 cm length range. Thus, for Scale A, available interval length = 15-3 = 12 cm

Duration of interval available for scale B = 15-3 = 12 cm

For scale C, usable interval length = 13 - 0 = 13 cm

Thus, (d) is the right choice.

Very Short Answer Type Questions

Question 10:  Correct the following.
(a) The motion of a swing is an example of rectilinear motion.
(b) 1 m = 1000 cm

Solution 10:  
(a) An example of periodic motion is the motion of a swing. Since, after a periodic interval of time, it repeats its motion.

(b) 1 m = 100 cm [each meter (m) has 100 equal divisions, referred to as centimeters (cm)]

Question 11: 

1. of an object or a part of it around a fixed point is known as ………. motion.
2. A body repeating its motion after certain interval of time is in ………… motion.
3. In rectilinear motion, object moves ………. a ……….. line.
4. The SI unit of length is ………. 

Solution 11:

1. Circular (An object moves in circular motion in such a way that its distance from a fixed point remains the same.)
2. Periodic, (e.g. motion of pendulum of wall clock.)
3. Along straight, (e.g. motion of a vehicle on a straight road.)
4. meter

Question 12:  Give one example for each of the following type of motion.

a)      Rectilinear

b)      Circular

c)       Periodic

d)      Circular and periodic

Solution 12:

a)      Motion of a stone falling from a height.

b)      Motion of a point marked on blades of a rotating fan.

c)       Motion of moon around the earth.

d)      Motion of hands of a clock.

Short Answer Type Questions

Question 13:  The photograph given in figure 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?

Solution 13:  The length of the grille’s straight iron bars is directly measured with a measuring tape. For curved iron bars, using a thread that can be further measured with the aid of measuring tape, the length can be measured.

Question 14:  Identify the different types of motion in the following word diagram given as in the figure.

Solution 14: The different types of motion in the following word diagram are as given:

Question 15:  Four children measure the length of a table which was about 2 m. Each of them used different ways to measure it.
(a) Shyam measured it with a half meter long thread.
(b) Gurmeet measured it with a 15 cm scale from her geometry box.
(c) Reena measured it using her hand span.
(d) 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.

Solution 15:  It will be most reliably calculated by Salim for the following reasons:

1. The length of 2 m that he wants to calculate can only be measured in one single attempt using this scale.

2. This scale is the default scale which will have the right calculation.

Other scales given are either non-standard or have a length smaller than the length we want to calculate.

Question 16:  Match the Column I with Column II.

Solution 16: The correct matching is as given:

(a) Rotational motion is a movement around a fixed axis in a circular path.

(b) Circular motion is the motion around a fixed point of an object or part of it.

(c) Periodic motion is a motion which, after a period of time, repeats itself.

Long Answer Type Questions

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.

Solution 17:   Trees along the track tend to be moving back when travelling (i.e. opposite the direction of motion of a train) since there is a relative shift between the outer trees and the moving train.

While the relative movement between us and co-passengers, in the case of co-passengers, is zero, they tend to be stationary.

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.

Solution 18:    Differences between wheel of moving bicycle and mark on the blade of electric fan are as follows:

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 difference in their measurements?
(Mention any three)

Solution 19: The reasons might be the following:

1. The scale length may not be right, i.e. the scale length may be shorter than the length that they want to calculate.
2. Their measurement scales may not be standard, or they may use different measurement scales.
3. There may be some mistakes in the scale they are using or they may not be using the right scale observation process.

Question 20:  Boojho was riding in his bicycle along a straight road. He classified the motion of various parts of the bicycle as (a) rectilinear motion (b) circular motion and (c) both rectilinear as well as circular motion. Can you list one part of the bicycle for each type of motion? Support your answer with reason.

Solution 20:

(a) Rectilinear motion: - The bicycle handle will still travel in a rectilinear direction as it is unable to perform circular or rotatory motion.

(b) Circular motion: - Without the whole chain system, bicycle pedals would still move circularly around their chain fixing system, as they will not move forward without the whole chain system.

(c) Both rectilinear and circular motion: - Bicycle wheels move in both rectilinear and circular motion, so the wheel as a whole will move forward and circular motion will be performed by its point or particles around the surface.