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Class 7 SCIENCE NCERT CHAPTER 13 SOLUTION

 CHAPTER 13

MOTION AND TIME


Here is some important points and answer of chapter 13 MOTION AND TIME NCERT science of class 7 which helps students to better understand topics of chapter 13 MOTION AND TIME.

1) Non-Uniform motion:- An object cover a proper distance in different time interval is known as Non- Uniform Motion.
2) Oscillation:- Movement by pendulum from its 'O' exists B point and B point to 'O' axis and again to A point and from A point to 'O' axis is known as Oscillation.
3) Simple Pendulum:- A simple pendulum consist a small metals ball, a thread and a stand.
4)Speed:- Distance covered by a vehicle in time is called speed.
5)Time period:-  Total time taken by an object for complete its task (work) is known as time period.
6)Uniform motion:- When an  object cover proper distance in definite time interval is known as Uniform Motion.
7) Speedometer:- Meter in vehicle which show its speed known as Speedometer.
8)Odometer:- Meter which show total distance covered by vehicle is called odometer.

These  are some important points about the Chapter 13 Motion And Time of Class 7 Science NCERT.

Here is the Solution Of Textbook Questions of Chapter 13 Motion And Time.

Exercise Questions-
Ques 1. Classify the following as motion along a straight line, circular or oscillatory motion.
i)Motion of your hands while running.
ii)Motion of a horse pulling a carton a straight road.
iii) Motion of a child in a merry-go-round.
iv) Motion of a child on a see-saw.
v) Motion of the hammer of an electric bell.
vi) Motion of a train on a straight bridge.

Ans. i) Oscillatory Motion
ii) Straight Line Motion
iii) Circular Motion
iv) Oscillatory Motion
v) Oscillatory Motion
vi) Straight line Motion

Ques 2. Which of the following are not correct?
i)The basic unit of time is second.
ii)Every object moves with a constant speed.
iii) Distances between two cities are measured in kilometres.
iv)The time period of a given pendulum is not constant.
v)The speed of a train is expressed in m/h.

Ans. Incorrect Statement are
ii) Every object moves with constant speed.
iv) The time period of a given pendulum is not constant.
v) The speed of a train is expressed in m/h.

Ques 3. A simple pendulum takes 32s to complete 20 oscillations. What is the time period of the pendulum?
Ans. Time taken by the pendulum to complete 20 oscillations in 32s.
Time period of the pendulum= T
Time period=Total Time Taken/ Number of Oscillations
Time period=32/20 =1.6 second

Ques 4. The distance between two stations is 240km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Ans. Distance between two stations=240 km
Time taken by the train to cover the distance =4 hours
Speed = Distance/Time
Speed=240/4
           =60km/h
Therefore, the speed of the train 60km/h.

Ques 5. The odometer of a car reads 57321.0km when the clock shows the time 8:30AM. What is the distance moved by  the car,if at 08:50AM, the odometer reading has changed to 57336.0km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.
Ans. Ist reading of odometer at 08:30AM. = 57321.0km
IInd reading of odometer at 08:50AM. =57336.0km
Total distance travelled= 57336.0km–57321.0km
                                           =15 km.
Total time taken= 08:50AM –08:30AM
                              =20min
Speed=Distance/Time
Speed=15km/20km =0.75km/min
We know, 60min =1hour
                                =20/60
               15km×3/1 = 45km/hr.

Ques 6. Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2m/s. Calculate the distance between her house and the school.
Ans. Salma takes total time=15 min
Salma's speed=2m/s
We know 1min=60 second
So, 15×60=900second
Speed=Distance/Time
So, distance=Time×Speed
                      =900×2m/s
                      =1800m/s
We know 1km=1000m
So, 1800/1000= 1.8km
 Distance of school from Salma's house
                        =1.8km

Ques 7.Show the shape of the distance time graph for the motion in the following cases.
 i) A car moving with a constant speed.
Ans. Shape of car on graph for motion in given case is.
CHAP-13-MOTION-AND-TIME




ii)A car parked on a side road.
Ans. Shape of car on graph for the motion is.
CHAP-13-MOTION-AND-TIME



Ques 8. Which of the following relations is correct?
i) Speed=Distance×Time
ii) Speed=Distance/Time
iii) Speed=Time/ Distance
iv) Speed=1/Distance ×Time.

Ans. ii)Speed =Distance/Time.

Ques 9.The basic unit of time is:
i)km/min
ii)m/min
iii)km/h
iv)m/s
Ans. iii)Km/h

Ques 10. A car moves with a speed of 40km/h for 15 minutes. The total distance covered by the car is:
i)100km
ii)25km
iii)15km
iv)10km

Ans. ii) 25km

Ques 11. Suppose the two photographs,shown in Fig. 13.1 and fig.13.2,had been taken at an interval of 10 seconds. If a distance of 100 metres is shown  by 1 cm in these photographs, calculate the speed of the blue car.
CHAP-13-MOTION-AND-TIME


Ans. Given 100m=1cm
Car moved 1.4cm =1.4×100= 140m 
 Time take by car =10second
Speed = Distance /Time
            =140/10= 14m/s 
As speed of the car is 14m/s

Ques 12. Fig. 13.15 shows the distance time graph for the motion of two vehicles A and B. Which one  of them is moving faster?
CHAP-13-MOTION-AND-TIME


Ans. According to the diagram, speed = Distance/time which marked A is with green colour and B is red colour. According to this, car A covered  more distance than car B in same time. So speed of car A will be faster.

Ques 13. Which of your following distance time graphs shows a truck moving with speed which is not constant?
CHAP-13-MOTION-AND-TIME






Ans.  iii) is the correct answer.

THE SOLUTION OF CHAPTER 13  MOTION AND TIME OF SCIENCE NCERT OF CLASS 7 IS GIVEN ACCORDING TO LATEST SYLLABUS CBSE 2020-2021. 




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