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**Ncert Exemplar Solutions Class 7 Science Motion and Time**

Welcome to NCTB Solutions. Here with this post we are going to help 7th class students for the Solutions of NCERT Exemplar Class 7 Science Book, Unit 13, Motion and Time. Here students can easily find step by step solutions of all the problems for Motion and Time, Also here our Science teacher’s are solved all the questions with easily understandable language with proper guidance so that all the students can understand easily.

**Motion and Time all Question Solutions :**

**Multiple Choice Questions :**

**Question no – (1)**

**Which of the following cannot be used for measurement of time?**

**Answer : **

The correct answer is option – (d)

Blinking of eyes cannot be used for measurement of time.

**Question no – (2)**

**Two clocks A and B are shown in Figure 13.1. Clock A has an hour and a minute hand, whereas clock B has an hour hand, minute hand as well as a second hand. Which of the following statement is correct for these clocks?**

**Answer : **

The appropriate answer is option – (c)

Time interval of 5 minutes can be measured by both A and B.

**Question no – (3)**

**Two students were asked to plot a distance-time graph for the motion described by Table A and Table B.**

**Answer : **

The correct answer is option – (a) both A and B.

**Question no – (4)**

**A bus travels 54 km in 90 minutes. The speed of the bus is**

**Answer : **

The correct answer is alternative – (b)

The speed of the bus is 10 m/s.

**Question no – (5)**

**If we denote speed by S, distance by D and time by T, the relationship between these quantities is**

**Answer : **

The correct answer is option – (c)

**Question no – (6)**

**Observe Figure 13.3.**

**Answer : **

The appropriate option is – (a)

The time period of a simple pendulum is the time taken by it to travel from A to B and back to A.

**Question no – (7)**

**Fig. 13.4 shows an oscillating pendulum**

**Answer : **

The correct option is – (d)

The time period of this simple pendulum is 4 (t_{1} + t_{2})

**Question no – (8)**

**The correct symbol to represent the speed of an object is**

**Answer : **

The appropriate option is – (a)

The correct symbol to represent the speed of an object is 5 m/s.

**Question no – (9)**

**Boojho walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds that the school is closed and comes back by a bicycle with his friend and reaches home in 20 minutes. His average speed in km/h is**

**Answer : **

The correct option is – (b)

His average speed will be 7.2 km/h.

**Very Short Answer Questions :**

**Question no – (11) **

**Answer : **

Since Boojho and Paheli covered unequal distances in same amount of time it would not be wrong to say that they were moving with different speed. The one who had to cover greater distance must have travelled with greater speed.

**Question no – (12) **

**Answer : **

As Boojho is travelling the same distance in less time than Paheli it must means that he is travelling with a greater speed than Paheli who needed 2 hours to cover the same distance.

**Short Answer Questions :**

**Question no – (13) **

**Answer : **

Distance (m) |
0 | 4 | 8 | 12 | 16 | 20 |

Time(s) |
0 | 2 | 4 | 6 | 8 | 10 |

**Question no – (14) **

**Answer : **

The average age of students in years = 12 years and 3 months

We know that 1 year has 365 days

So 12 years = 12 × 365 = 4380 days

We know that 1 month has 30 days

So 3 months = 30 × 3 = 90 days

total number of days = 4380 + 90 = 4470 days

We know that 1 day has 24 × 60 × 60 = 86400 seconds

Therefore, 4470 expressed in seconds

= 4470 × 86400

= 386208000 seconds

**Question no – (15) **

**Answer : **

Given, Speed = 36000 km/ hr

Time (in hours) taken to cover distance= 1 hr

Time ( in seconds) taken to cover distance

= 1 × 60 × 60

= 3600 secs

We know that Speed = Distance/ Time

So speed( in secs) = 36000/3600

= 10 km/s

**Long Answer Questions :**

**Question no – (18) **

**Answer : **

**(a)** By looking at the graph we could clearly say that the position of the object at 20 seconds is 8 meters.

**(b)** It can be seen in the graph that the object travelled 6 m in 12 seconds.

**(c)** The average speed of the object is the total distances covered by the object divided by the total time taken to cover those distances.

So Average Speed will be,

= 8/20

= 0.4 m/ s

**Question no – (20) **

**Answer : **

**(a)** The graph between point B and C indicates that Boojho is not moving and that his speed is zero. It is due to the reason that the graph between B and C is parallel to the time axis.

**(b)** The motion of Boojho in 0 to 4 minutes is not uniform as the distance time graph is not a straight line.

**(c)** The speed in 8 to 12 minutes of the journey = Distance / Time

Distance = 225 – 150 = 75 km

Time taken = 12- 8 = 4 minutes

Therefore, Speed = 75/4 = 1875 km/ min

**Other Chapter Solutions : **

👉 Heat

👉 Physical and Chemical Changes

👉 Weather, Climate and Adaptation of Animals to Climate

👉 Soil

👉 Transportation in Animals and Plants

👉 Electric Current and Its Effects

👉 Light

👉 Wastewater Story