# NCERT Solutions for Class 7 Science Chapter 13 Motion and Time

**NCERT solutions for class 7 science chapter 13 Motion and Time: **After completing a chapter it is necessary to practice the questions given in the book. NCERT Solutions for class 7 science chapter 13 motion and time helps students in solving the homework questions. Earlier you have learnt about different types of motions. You learnt the motion along a straight line, circular path and periodic motion. The first question explained in the NCERT solutions for class 7 science chapter 13 motion and time is based on these classifications. You know that some vehicles move faster than others. If you know the distance covered by two buses in one hour, it is easy to tell which one is faster. The distance covered by an object per unit time as the speed. All you will study in this chapter is the speed and time measurements. NCERT solutions for class 7 science chapter 13 motion and time is helpful in scoring good marks in the examination. NCERT Solutions is an essential tool for the preparation of the exam. Students are recommended to go through NCERT solutions for class 7 to score high marks in their examination.

** Here are the important topics of NCERT class 7 science chapter 13 motion and time **

13.1 Slow or Fast

13.2 Speed

13.3 Measurement of Time

Units of Time and Speed

13.4 Measuring Speed

13.5 Distance-time Graph

If you have any problem in answering the exercise questions or you are not getting the correct answers then don't worry, NCERT solutions for class 7 science chapter 13 motion and time is there for you to help.

## ** Solutions of NCERT for class 7 chapter 13 motion and time exercise: **

1. Classify the following as motion along a straight line, circular or oscillatory motion:

** Answer: **

(i) Oscillatory motion

While running, our hands move in back and forth direction and repeat its movement after some time. Hence it is an oscillatory motion.

(ii) Motion along the straight line-

A horse is pulling a cart on a straight road. Therefore it follows the motion along a straight line.

(iii) Circular motion-

Since the merry-go-round moves in a circular motion

(iv) Oscillatory motion-

The see-saw moves up and down continuously. It oscillates up-down.

(v) Oscillatory motion

(vi) Motion along a straight line-

The train is moving on a straight bridge. Therefore it follows the motion along the straight line.

** 2. ** Which of the following are not correct?

** Answer: **

The option (ii), (iv) and (v) are not correct.

(ii) The object can move with variable or constant speed.

(iv) The time period of a pendulum depends on the length of the thread. So, it is constant for a particular length.

(v) Speed of train is measured either in km/h or m/s not in m/h

** 3 ** . A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

** Answer: **

Given that,

A simple pendulum takes 32 s to complete 20 oscillations. It means,

No. of oscillation = 20, and

Total time is taken = 32 s

According to question,

Time period = (T)

** Answer: **

Given that,

Distance between the two stations = 240 km

and, time taken = 4 hour

Therefore, Speed = Distance / Time

= 240/4

= 60 km/h

** Answer: **

We have,

The initial reading of odometer = 57321 km

The final reading of odometer = 57336 km

So, distance covered by the Car = Final reading - Initial reading = 15 km

The total time taken by the car to travel 15 km = 8:50 AM - 8:30 AM = 20 min

According to question,

Speed of the car = Distance / time taken = 15/20 = 0.75 km/min

Again, 60 minute = 1 hr

so, 1 min = 1/60 hr

Speed in terms of km/hr =

** Answer: **

Given that,

time taken by Salma to reach her school from house = 15 min =

and, speed of the bicycle = 2 m/s

It is known that,

Distance covered = Speed time taken

= 1.8 km

** 7 ** . Show the shape of the distance-time graph for the motion in the following cases:

(i) A car moving with a constant speed.

(ii) A car parked on a side road.

** Answer: **

(i) A car is moving with a constant speed covers equal distance in equal interval of time. Therefore,

(ii) Distance-time graph of a car parked on a roadside is such that an increase in time, there is no change in distance.

** 8 ** . Which of the following relations is correct?

** Answer: **

The option (ii) is the correct answer.

Speed = distance /time , this relation holds correctly

** 9. ** The basic unit of speed is:

(i) km/min (ii) m/min (iii) km/h (iv) m/s

** Answer: **

The option (iv) is the correct answer.

The SI unit of speed is m/s (meter per second)

(i) 100 km (ii) 25 km (iii) 15 km (iv) 10 km

** Answer: **

The correct option is (ii)

Answer = 25 km

1st case,

Speed = 40 km/hr

and time taken = 15 min

So, distance =

Case 2nd,

Speed = 60 km/h

Time taken = 15 min = 0.25 h

So, Distance travelled =

So, total distance = 15 + 10 = 25 km

Answer:

Given, Scale:

The blue car is the fastest.

Distance travelled by the blue car in the picture=

Therefore, the actual distance travelled by blue car =

Time taken =

Speed of the blue car =

Therefore, Speed of the blue car is

** Answer: **

It is known that, ** (speed = distance/time) **

it means greater the speed, more distance is covered by the car in a given interval of time.

From the graph, we can see that The distance covered by the vehicle A is more than the vehicle B. Hence A is faster than B.

** 13. ** Which of the following distance-time graphs shows a truck moving with a speed which is not constant?

** Answer: **

The correct option is (iii)

- In graphs, the constant speed is shown by a straight line.
- A straight line parallels to the time axis, it indicates that the body is at rest position.
- A curved line on graphs means the speed is not constant.

** Chapterwise NCERT solutions of class 7 science **

** **

** NCERT Solutions for Class 7 Subject Wise **

** Important formulas: **

The numerical problems discussed in the NCERT solutions for class 7 science chapter 13 motion and time is based on the following formulas.

- Time period

- Questions based on the distance-time graph are also discussed in the NCERT solutions for class 7 science chapter 13 motion and time .

## Frequently Asked Question (FAQs) - NCERT Solutions for Class 7 Science Chapter 13 Motion and Time

**Question: **Whether the class 7 science chapter 13 motion and time is useful in higher studies ?

**Answer: **

Yes, this chapter is very important for higher studies in the field of science and technology

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