NCERT Solutions for Class 7 Science Chapter 13 Motion and Time are part of NCERT Solutions for Class 7 Science. 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).

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