Ncert exemplar solutions science class 7 Solutions for Chapter 13 motion and time

Exercises in Chapter 13 motion and time Grade 7

Motion and Time – Exercise

Questions in Motion and Time – Exercise

Which of the following cannot be used for measurement of time?

(a) A leaking tap.

(b) Simple pendulum.

(d) Blinking of eyes.

Two clocks A and B are shown in Figure 13.1. Clock A has an hour and a minute hand, whereas clock B has an hour hand, minute hand as well as a second hand. Which of the following statement is correct for these clocks?

(a) A time interval of 30 seconds can be measured by clock A.

(b) A time interval of 30 seconds cannot be measured by clock B.

(d) Time interval of 4 minutes 10 seconds can be measured by clock A.

Two students were asked to plot a distance-time graph for the motion described by Table A and Table B.

The graph given in Figure 13.2 is true for

(a) both A and B.

(b) A only.

(d) neither A nor B.

A bus travels 54 km in 90 minutes. The speed of the bus is

(a) 0.6 m/s

(b) 10 m/s

(d) 3.6 m/s

If we denote speed by S, the distance by D and time by T, the relationship between these quantities is

(a) S = D × T

(b) T = S/D

Observe Figure 13.3.

The time period of a simple pendulum is the time taken by it to travel from

(a) A to B and back to A.

(b) O to A, A to B and B to A.

(d) A to B.

Fig. 13.4 shows an oscillating pendulum

Time taken by the bob to move from A to C is t1 and from C to O is t2. The time period of this simple pendulum is

(a) (t1 + t2 )

(b) 2 (t1 + t 2 )

(d) 4 (t1 + t 2 )

The correct symbol to represent the speed of an object is

(a) 5 m/s

(b) 5 mp

(d) 5 s/m

Boojho walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds that the school is closed and comes back by bicycle with his friend and reaches home in 20 minutes. His average speed in km/h is

(a) 8.3

(b) 7.2

(d) 3.6

A simple pendulum is oscillating between two points A and B as shown in Figure 13.5. Is the motion of the bob uniform or non-uniform?

Paheli and Boojho have to cover different distances to reach their school but they take the same time to reach the school. What can you say about their speed?

If Boojho covers a certain distance in one hour and Paheli covers the same distance in two hours, who travels at a higher speed?

Complete the data of the table given below with the help of the distance-time graph given in Figure 13.6.

The average age of children of Class VII is 12 years and 3 months. Express this age in seconds.

A spaceship travels 36,000 km in one hour. Express its speed in km/s.

Starting from A, Paheli moves along a rectangular path ABCD as shown in Figure 13.7. She takes 2 minutes to travel each side. Plot a distance-time graph and explain whether the motion is uniform or non-uniform.

Plot a distance-time graph of the tip of the second hand of a clock by selecting 4 points on x-axis and y-axis respectively. The circumference of the circle traced by the second hand is 64 cm.

Given below as Figure 13.8 is the distance-time graph of the motion an object.

(i) What will be the position of the object at the 20s?

(ii) What will be the distance travelled by the object in 12s?

(iii) What is the average speed of the object?

Distance between Bholu’s and Golu’s house is 9 km. Bholu has to attend Golu’s birthday party at 7 o’clock. He started from his home at 6 o’clock on his bicycle and covered a distance of 6 km in 40 minutes. At that point, he met Chintu and he spoke to him for 5 minutes and reached Golu’s birthday party at 7 o’clock. With what speed did he cover the second part of the journey? Calculate his average speed for the entire journey.

The speed with which Bholu covered the second part of the journey.

Boojho goes to the football ground to play football. The distance-time graph of his journey from his home to the ground is given as Figure 13.9.

(a) What does the graph between point B and C indicate about the motion of Boojho?

(b) Is the motion between 0 to 4 minutes uniform or nonuniform?