Notes of chapter: Motion and Time are presented below. Indepth notes along with worksheets and NCERT Solutions for Class 7.
(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 cart on a straight road
(iii) Motion of a child in a merry- go – round.
(iv) Motion of a child in a see-saw.
(v) Motion of a hammer of an electric bell.
(vi) Motion of a train on a straight bridge.
Ans-
| S.N. | Example of motion | Type of motion |
| 1. | Motion of your hands
while running |
Oscillatory |
| 2. | Motion of a horse pulling a cart on a straight road. | Straight line |
| 3. | Motion of a child in a merry- go – round.
|
Oscillatory, Circular |
| 4. | Motion of a child in a see-saw. | Oscillatory |
| 5. | Motion of a hammer of an electric bell. | Oscillatory |
| 6. | Motion of a train on a straight bridge. | Straight line |
(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 kilometers.
(iv) The time period of a given pendulum is not constant.
(v) The speed of a train is expressed in m/s.
Ans – The sentences which are not correct is given below:
(ii) Every object moves with a constant speed.
(iv)The time period of a given pendulum is not constant.
(v) The speed of a train is expressed in m/s.
(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.
Ans-
(i) The shape of the distance – time graph for a car moving with a constant speed will always be straight line because car travel equal distance in equal interval of time. The graph is shown below:
(ii) The shape of the distance – time graph for a car parked on a road side will always be horizontal straight line parallel to time axis(x axis) because car is not travelling any distance with the increase of time. The graph is shown below:
(9) The basic unit of speed is;
(i) km/min
(ii) m/min
(iii)km/h
(iv)m/s
Ans-
(i) km/min
(ii) m/min
(iii)km/h
(iv)m/s √
(10) A car moves with a speed of 40 km/h for 15min and then with a speed of 60km/h for the next 15 minutes. The total distance covered by the car is:
(i) 100km
(ii) 25km
(iii) 15km
(iv)10km
Ans-
The speed of the car in first 15 min = 40 km/h
Time taken by car = 15 min
= 15/60
= .25 hour
Distance travelled by car in first 15 min = Time × Speed
= .25 × 40
= 10.00 km
The speed of the car in second 15 min = 60 km/h
Distance travelled by car in second 15 min = Time × Speed
= .25 × 60
= 15.00 km
Total distance = 10 +15
= 25 km
(12) Figures given below shows the distance – time graph for the motion of two vehicles A and B. Which one of them is moving faster?
Ans-
Draw a perpendicular CD on time axis to know the distance travelled by cars. It is clear from the figure that A travelled dA distance which is more than distance dB travelled by B.
(13) Which of the following distance – time graphs shows a truck moving with speed which is not constant?
(i)
(ii)
(iii)
(iv)
Ans–
(iii) is required answer because it shows non constant movement of truck.
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