NCERT Solutions Class 7th Science Chapter – 9 Motion and Time Question & Answer

May 11, 2022

NCERT Solutions Class 7th Science Chapter – 9 Motion and Time

Textbook	NCERT
Class	7^th
Subject	Science
Chapter	9^th
Chapter Name	Motion and Time
Category	Class 7th Science
Medium	English
Source	Last Doubt

NCERT Solutions Class 7th Science Chapter – 9 Motion and Time

Chapter – 9

Motion and Time

Question & Answer

Q. 1. Classify the following as motion along a straight line, circular or oscillatory motion :
(i) Motion of your hands while running.
Answer: Oscillatory motion

(ii) Motion of a horse pulling a cart on a straight road.
Answer: Linear motion

(iii) Motion of a child in a merry-go-round.
Answer: Circular motion

(iv) Motion of a child on a see-saw.
Answer: Oscillatory motion

(v) Motion of the hammer of an electric bell.
Answer: Oscillatory motion

(vi) Motion of a train on a straight bridge.
Answer: Linear motion

Q. 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/h
Answer: (ii), (iv), (v)

Q. 3. A simple pendulum takes 32s to complete 20 oscillations, what is the time period of the pendulum?
Answer: Time taken to complete 20 oscillations = 32 s
Time taken to complete 1 oscillation = 32/20 s = 1.6 s
Time period of a pendulum is time taken by it to complete 1 oscillation.
Time period of pendulum is 1.6 seconds.

Q. 4. The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.
Answer:
Distance = 240 km
Time taken = 4 hours
Speed =Distance covered/time taken = 240km/4 hammer
=60 km/h
Speed of train =60 km/h

Q. 5. The odometer of a car reads 57321.0 km when the clock shows the time 08:30 AM. What is the distance moved by the car, if at 08:50 AM, the odometer reading has changed to 57336.0 km? Calculate the speed of the car in km/min during this time. Express the speed in km/h also.
Answer: Distance = 57336.0 km – 57321 km =15 km
Speed in km/min =15km/20 min = 3/4 km/min

Speed in km/hr =15 km/1/3 hr
=(15 x 3) km/hr
=45 km/hr.

Q. 6. Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/min, calculate the distance between her house and the school.
Answer: Time taken =15 min
Speed = 2 m/min.
Distance = speed x time = 2 x 15 = 30 m
Distance between Salma’s school and her house is 30 m.

Q. 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
Answer: (ii) Speed = Distance/Time is correct

Q. 9. The basic unit of speed is:
(i) km/min
(ii) m/min
(iii) km/h
(iv) m/s
Answer: (iv) m/s

Q. 10. 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. The total distance covered by the car is:
(i) 100 km (ii) 25 km (iii) 15 km (iv) 10 km
Answer: (ii) 25 km

Q. 11. Suppose the two photographs, shown in fig. 13.1 and fig. 13.2 of NCERT 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.
Answer: 0.1 cm/s or 10 m/s