DAV Class 7 Science Book Solutions Chapter 6: Here you will get the complete question answer for DAV Class 7 Science Book Chapter 6 Motion and Time. With the help of these solutions for DAV Class 7 Science the Living World book, you can easily grasp basic concepts better and faster.
DAV Class 7 Science Book Solutions Chapter 6
Highlights
- A. Fill in the blanks.
- B. True or False.
- C. Tick the correct option.
- D. Answer the following questions in brief.
- E. Answer the following questions.
A. Fill in the blanks.
1. An object is said to be at rest if it ___________ change its position with time.
2. The SI unit of time is ___________.
3. A child, sitting in a revolving giant wheel, is an example of a ___________ motion.
4. A car, moving on a busy straight road, is an example of ___________ motion.
5. The speedometer of a motorbike measures its speed in ___________.
Answer: (1) does not (2) second (3) circular (4) non uniform or linear (5) km/h
B. Write True or False for the following statements.
1. The speed of a fast moving train is usually measured in metre per hour.
2. The average speed remains constant for an object having a uniform motion.
3. A man walks for 1 minute, at a speed of 1 m/s, along a straight track. The total distance covered by him is 1 m.
4. An object, moving along a straight line, is said to be in uniform motion if it covers regularly increasing distances in equal intervals of time.
5. The time period of a simple pendulum, that takes 42 seconds to complete 20 oscillations, equals 2.1 seconds.
6. The distance-time graph, for a car kept parked on a side road, is a straight line parallel to the time axis.
Answer: (1) False (2) True (3) False (4) False (5) True (6) True
C. Tick the correct option.
Answer:
1. distance = speed x time
2. 30 minutes
3. 15 km
4. option (a)
5. 4 (t1+t2)
6. m/second
D. Answer the following questions in brief.
Q. 1. A boy walks to his school with a constant speed of 4 km/h and reaches there in 30 minutes. Find the distance of the school from his house.
Answer:
Speed = 4 km/h
Time taken = 30 minutes = ½ h = 0.5 h
Therefore,
Distance = speed x time
= 4 km/h x ½ h
= 2 km
Hence, distance of school from his house is 2 km.
Q. 2. The distance between two stations is 216 km. A bus takes 4 hours to cover this distance. Calculate the average speed of the bus in km/hour.
Answer:
Q. 3. Two Cars, A and B. (starting, at the same time, from the same point) are moving with average speeds of 40 km/h and 50 km/h, respectively, in the same direction. Find how far will Car B be from Car A after 3 hours.
Q. 4. A car moves with a speed of 40 km/h for 15 minutes and then with a speed of 60 km/h for the next 15 minutes. Find the total distance covered by the car in these 30 minutes.
Answer:
Distance covered in 1st 15 minutes = 40 km/h x 15 minutes
= 40 km/h x ¼ h
= 10 km
Distance covered in 2nd 15 minutes = 60 km/h x 15 minutes
= 60 km/h x ¼ h
= 15 km
Therefore, Total distance covered = 10 km + 15 km
= 25 km
Q. 5. Define the term ‘Periodic motion. Give two examples of periodic motions that can be used to measure time.
Answer:
Periodic motion – motion, which repeats itself after a regular interval of time, is called periodic motion.
Examples: (1) motion of the hands of a clock.
(2) motion of the moon around the earth.
Q. 6. Distinguish between uniform and non-uniform motion. Give one example of each.
Answer:
Uniform motion
An object is said to be in uniform motion when it moves along a straight path, and covers equal distances in equal intervals of time, howsoever small these intervals of time may be.
Example: Motion of a body along a straight path covering equal distances in equal intervals of time.
Non-uniform motion
When an object, (1) moving along a straight path, covers unequal distances in equal intervals of time or (2) does not move along a straight path, its motion, is called a non-uniform motion.
Example: Motion of a free-falling object.
Q. 7. Draw the shape of distance-time graph for:
(a) a man, waiting for a bus, standing at one point, on a bus-stand.
Answer:
(b) a man, walking on a level, straight and narrow road, with a constant speed.
Answer:
E. Answer the following questions.
Answer 1:
Motion of the farmer – non-uniform, as he covers unequal distances in equal intervals of time.
Average speed of the farmer = total distance covered/time taken
= 240 m/16 min.
= 240 m / 960 seconds {change min. into second}
= ¼ m/s
= 0.25 m/s
Answer 2:
Speed of sound = 340 m/s
Time taken = 6 seconds
Therefore, distance = 340 m/s x 6 seconds
= 2040 m
= 2.04 km
Hence, thundering sound was produced at a distance of 2.04 km from Shivam.
Answer 3:
(a) A simple pendulum can be made by a metal ball attached to taut light string, or thread, that is fixed rigidly at one end.
(b) Number of complete oscillations = 5
Total time taken = 10 seconds
Time period of the pendulum = 10/5 = 2 seconds
Answer 4:
Object A is in uniform motion as it covers equal distances in equal intervals of time.
Object B is in non-uniform motion as it does not cover equal distances in equal intervals of time
Answer 5:
(1) Value of ‘P’ = 3 m, Value of ‘Q’ = 12 m
(2) Value of ‘R’ = 12 seconds
thanku so much
Thank u so much sir
This is very help full
Thanks who invent this link this is very use ful for any d
av student
This is very helpful and thanks.
It is really a useful link…it really helped a lot! Now gonna use it…
Very good.No need of any tution
It is very helpful to the parents as well as students to get the exact precise answer of the particular question.
Yes it is very very helpful to me
THANKS
Nice and useful
It is very useful for exams. My exam is tomorrow but my work is not complete but,this link help me a lot. Thankyou solution Gyan
Thank you sir very much for it
Namaste elvish Bhai
And
Thank you solution gyan
Thank you sir