# Here we have given NCERT Solutions for Class 7 Science Chapter 13 Motion and Time.

Board | CBSE |

Textbook | NCERT |

Class | Class 7 |

Subject | Science |

Chapter | Chapter 13 |

Chapter Name | Motion and Time |

Number of Questions Solved | 13 |

Category | NCERT Solutions |

## NCERT Solutions for Class 7 Science Chapter 13 Motion and Time

Question 1.

Classify the following as motion along a straight line, circular or oscillatory motion :

- Motion of your hands while running.
- Motion of a horse pulling a cart on a straight road.
- Motion of a child in a merry-go-round.
- Motion of a child on a see-saw.
- Motion of the hammer of an electric bell.
- Motion of a train on a straight bridge.

Solution:

- oscillatory
- straight line
- circular
- oscillatory
- oscillatory
- straight line.

Question 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.

Solution:

(ii) , (v).

Question 3.

A simple pendulum takes 32 s to complete 20 oscillations. What is the time period of the pendulum?

Solution:

Time taken for 20 oscillations = 32 s

Time taken for 1 oscillation =

Hence, Time period = 1.6 s

Question 4.

The distance between two stations is 240 km. A train takes 4 hours to cover this distance. Calculate the speed of the train.

Given, distance = 240 km,

time = 4 h,

speed = = = 60 km/h.

Question 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.

Solution:

Question 6.

Salma takes 15 minutes from her house to reach her school on a bicycle. If the bicycle has a speed of 2 m/s, calculate the distance between her house and the school.

Solution:

Given, Speed = 2 m/s

Time =15 min = 15 x 60 s = 900 s

distance = speed x time

= 2 m/s x 900 s = 1800 m

km

= 1.8 km

Question 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.

Solution:

(i) A car moving with a constant speed covers equal distance in equal intervals of time

(ii) The distance-time graph of a car parked on a road side is such that with the increase in time, there is no change in distance.

Question 8.

Which of the following relations is correct?

(i) Speed = Distance x Time

(ii) Speed =

(iii) Speed =

(iv) Speed =

Solution:

(ii) Speed =

Question 9.

The basic unit of speed is :

(i) km/min

(ii) m/min

(iii) km/h

(iv) m/s

Solution:

(iv) m/s

Question 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

Solution:

Distance travelled in first 15 min

= speed x time

= 40 km/h x 15 min

= 40 km/h x 15/60 h = 10 km

Distance travelled in last 15 min

= speed x time

= 60 km/h x 15 min

= 60 km/h x 15/60 h = 15 km

Total distance = (10 +15) km = 25 km

Hence, option (ii) is correct.

Question 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.

Solution:

Speed = 100 m/10 s = 10 m/s

Question 12.

shows the distance-time graph for the motion of two vehicles A and B. Which one of them is moving faster?

Solution:

Vehicle A is moving faster.

Question 13.

Which of the following distance-time graphs shows a truck moving with speed which is not constant?

Solution:

Graph (iii)

### NCERT Solutions for Class 7 Science

- Chapter 1 Nutrition in Plants
- Chapter 2 Nutrition in Animals
- Chapter 3 Fibre to Fabric
- Chapter 4 Heat
- Chapter 5 Acids, Bases and Salts
- Chapter 6 Physical and Chemical Changes
- Chapter 7 Weather, Climate and Adaptations of Animals to Climate
- Chapter 8 Winds, Storms and Cyclones
- Chapter 9 Soil
- Chapter 10 Respiration in Organisms
- Chapter 11 Transportation in Animals and Plants
- Chapter 12 Reproduction in Plants
- Chapter 13 Motion and Time
- Chapter 14 Electric Current and its Effects
- Chapter 15 Light
- Chapter 16 Water A Precious Resource
- Chapter 17 Forests: Our Lifeline
- Chapter 18 Wastewater Story

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