# Motion and Time| NCERT Solutions| Class 7

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.

Helping Topics

Motion

Worksheet Class 7

Displacement

Distance

Time

Acceleration