RBSE Class 7 Science Important Questions Chapter 13 Motion and Time

Rajasthan Board  RBSE Class 7 Science Important Questions Chapter 13 Motion and Time Important Questions and Answers.

RBSE Class 7 Science Chapter 18 Important Questions Motion and Time

Multiple Choice Questions

Question 1.
A sundial can be used :
(a) on a sunny day 
(b) at night 
(c) on a cloudy day
(d) any time
Answer:
(a) on a sunny day 

Question 2. 
Which one of the following is used for measuring small intervals of time?
(a) Digital clock 
(b) Stopwatch
(c) Hourglass 
(d) Wrist watch
Answer:
(b) Stopwatch

Question 3. 
Pick the odd one out:
(a) decade 
(b) century
(c) millennium 
(d) second
Answer:
(d) second

Question 4. 
Which of the following does not show periodic motion?
(a) Pendulum 
(b) Hands of a clock
(c) Revolution of the earth around the sun
(d) A car moving at a constant speed
Answer:
(d) A car moving at a constant speed

Question 5. 
A bus travels 54 km in 90 minutes, the speed of the bus is :
(a) 0.6 m/s 
(b) 10 m/s
(c) 5.4 m/s 
(d) 3.6 m/s
Answer:
(b) 10 m/s

Question 6. 
The correct symbol to represent the speed of an object is :
(a) m/s 
(b) m
(c) s 
(d) s/m
Answer:
(a) m/s 

Fill in the blanks

Question 1. 
The suspended metallic ball of a pendulum is called its.....................
Answer:
bob

Question 2. 
One nanosecond is.....................of a second. 
Answer:
one billionth

Question 3. 
Higher the speed, of a body traveling
along a straight line,.....................will be the distance covered by it.
Answer:
more

Question 4. 
The principle of.....................motion is used in a pendulum clock.
Answer:
oscillatory

Question 5. 
To and fro motion is called.....................
Answer:
oscillatory motion

State Whether True or False

Question 1. 
Age can be conveniently expressed in days and hours.
Answer:
False

Question 2. 
The second is the basic unit of time.
Answer:
True

Question 3. 
The motion of the simple pendulum is circular.
Answer:
False

Question 4. 
The speed of a train is expressed in terms of m/h.
Answer:
False

Question 5. 
The symbols of all units are written in the singular.
Answer:
True

Match the following

Column I	Column II
10 decades	(a) Electric circuit
SI unit of speed	(b) Distance of vehicle
10 centuries	(c) Time to complete one oscillation
Oscillatory motion	(d) Graph
Bob	(e) To and fro motion
Odometer	(f) Century
Speedometer	(g) Metallic ball
Time period	(h) m/s
Quartz dock	(i) Millennium
Origin	(j) Speed of vehicle

Answer:

Column I	Column II
10 decades	(f) Century
SI unit of speed	(h) m/s
10 centuries	(i) Millennium
Oscillatory motion	(e) To and fro motion
Bob	(g) Metallic ball
Odometer	(b) Distance of vehicle
Speedometer	(j) Speed of vehicle
Time period	(c) Time to complete one oscillation
Quartz dock	(a) Electric circuit
Origin	(d) Graph

Very Short Answer Type Questions

Question 1. 
What is the difference when we walk fast and slow?
Answer:
The difference is that when we walk fast, we cover more distance in less time as compared to when we walk slowly.
 
Question 2. 
Paheli and Boojho have to cover the different distances to reach their school but they take the same time to reach the school. What can you say about their speed?
Answer:
Paheli and Boojho have different speeds.

Question 3. 
What is the basic unit of time? 
Answer:
The basic unit of time is second.

Question 4. 
What is measurement?
Answer:
Measurement is defined as the comparison of an unknown quantity with a known quantity of the same kind.

Question 5. 
Name some common clock.
Answer:
Some common docks are wall dock, table dock, and digital clock.

Question 6. 
What devices do we use to measure intervals of time which are much shorter than a day?
Answer:
The most common time measuring devices used are docks or watches.

Question 7. 
What is an oscillatory motion? 
Answer:
The to and fro motion of a simple pendulum is called oscillatory motion.

Question 8. 
What are quartz clocks?
Answer:
The docks or watches having an electric circuit with ope or more cells are called quarts docks. ...

Question 9. 
Name the device used to measure speed.
Answer:
Speedometer.

Question 10. 
Name the device used to measure distance.
Answer:
Odometer.

Question 11. 
Write the formula used to measure distance.
Answer:
Distance = Speed x Time

Question 12. 
Where will you find speedometers and odometers?
Answer:
Speedometers and odometers will be seen on the dashboards of buses, cars, and other vehicles.

Question 13. 
What is the smallest time interval that can be measured with commonly available clocks and watches?
Answer:
Seconds

Question 14. 
What is a nanosecond?
Answer:
A nanosecond is one billionth of a second.

Question 15. 
What are the various types of graphs?
Answer:
Pie chart, bar graph, and line graph.

Short Answer Type Questions

Question 1. 
Assume you start pedaling your bicycle at the same time as he begins to move. The distance covered by the bus is more than that of yours at the same time. Would you say that bus is moving faster than the bicycle?
Answer:
The faster vehicle has a higher speed. One who takes the shortest time to cover the given distance has the highest speed. So, we will say that he is moving faster than the bicycle.

Question 2. 
If Boojho covers a certain distance in one hour and paheli covers the same distance in two hours, who has traveled at a higher speed?
Answer:
Boojho has traveled at a higher speed as he covers the same distance in a lesser time than paheli.

Question 3. 
Define the speed of the object.
Answer:
The distance covered by an object in a unit of time is the speed of the object.
Distance covered


Question 4. 
Give two examples of uniform motion.
Answer:

1. Car moving on a straight road without any traffic.
2. The motion of the earth around the sun.

Question 5. 
Give two examples of non-uniform motion.
Answer:

1. A car moving in heavy traffic.
2. The bus takes a turn.

Question 6. 
Siya takes 40 seconds to run around her school ground path 200 m. Calculate her speed.
Answer:
Distance covered by Siya = 200 m Time taken = 40 s

\(=\frac{200}{40}=5 \mathrm{~m} / \mathrm{s}\)

Question 7. 
Convert 36 km/h into m/s.
Answer: 
To convert 36 km/h into m/s
Multiply by\(\frac{5}{18}\)

1 km = 1000 m and 1 hour = 3600 s

\(\frac{1 \mathrm{~km}}{1 \text { hour }}=\frac{1000}{3600}=\frac{5}{18} \mathrm{~km} / \mathrm{h}\)

=36×\(\frac{5}{18}\)m/s

Question 8. 
Convert 20 m/s into km/h.
Answer: 
To convert 20 m/s into km/h Multiply by \(\frac{18}{5}\)
\(=20 \times \frac{18}{5}=72 \mathrm{~km} / \mathrm{h}\)

Question 9. 
A spaceship travels 36,000 km in one hour, expressing its speed in km/s. 
Answer:
Speed of spaceship = 36,000 km/h To convert hours into seconds
1 hour = 60 x 60 second 

\(=\frac{36000}{1 \times 60 \times 60}=10 \mathrm{~km} / \mathrm{s}\)

Question 10. 
What do you understand by periodic motion?    
Answer:
The motion that repeats itself in regular intervals of time is called periodic motion. For example - The rotation of the earth on its axis, and the revolution of the earth around the sun.

Question 11. 
Boojho is wondering how many seconds are there in a day and how many hours in a year?
Answer:
1 day = 24 hours x 60 minutes x 60 seconds= 86400 seconds 1 year = 365 days x 24 hours = 8760 hours

Question 12. 
A train is traveling at a speed of 100 km/hour. How long will it take to complete a journey of 500 km without any stoppage? 

Distance = 500 km

\(=\frac{500}{100}=5 \text { hours }\)
 

Question 13.
A train is traveling at a speed of 120 km/h. How long will it take to travel 360 km?
Answer:

\(=\frac{360}{120} \text { hours }=3 \text { hours }\)

The train will take 3 hours to travel 360 km.

Long Answer Type Questions

Question 1. 
Write the difference between uniform and non-uniform motion. 
Answer: 
Difference between uniform and non-uniform motion :

Uniform motion	Non-uniform motion
An object moving along a straight line with a constant speed is said to be in uniform motion.	If the speed of an object moving along a straight line keeps changing, its motion is said to be non­uniform motion.

Speed = 50 km/h; time = 5 h

\(50=\frac{\text { Distance covered }}{5}\)

Distance covered = 50 kip/h x 5 h = 250 km.

Question 3.
A bus travels 54 km in 90 minutes. What is the speed of the bus?
Answer:
Distance traveled by bus = 54 km Time taken - 90 minutes
Time is taken in hours\(=\frac{90}{60}=\frac{3}{2} \text { hours }\)

\(=\frac{54 \times 2}{3}=36 \mathrm{~km} / \mathrm{h}\)

Question 4. 
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. What is his average speed in km/h?
Answer:
Average speed

Total distance covered

= 3km + 3km = 6km
Total time taken

= 30 minutes + 20 minutes

= 50 Minutes = \(\frac{50}{60} \text { hours }\)

\(=\frac{5}{6} \text { hours }\)

\(=\frac{6 \times 6}{5}=\frac{36}{5}\)

= 7.2 km/h

Question 5. 
How did ancestors measure a day month and year?
Answer:
Our ancestors noticed that many events in nature repeat themselves after regular definite intervals of time. By looking at the regular events they were able to predict the day, month, and year.

• The time between one sunrise and the next was called a day.
• A month was measured from one new moon to the next.
• A year was measured as the time taken by the earth to complete one revolution.

Question 6.
Rockets launching satellites into the Earth’s orbit often attains speed up to 8 km/s, on the other hand, a tortoise can move only at the speed of 8 cm/s. Can you calculate how fast the rocket moved compared with the tortoise?
Answer: 
Speed of the rocket = 8 km/s 
Speed of the rocket in m/s = 8x 1000 m/s
= 8000 m/s 
1 km = 1000 m 
Speed of the tortoise = 8 cm/s 
Speed of the tortoise in m/s

\(=\frac{8}{100} \mathrm{~m} / \mathrm{s}=0.08 \mathrm{~m} / \mathrm{s}\)

Different in the speed of the rocket and tortoise    = (8000 - 0.08) m/s
= (7999.92 m/s)
Rocket is faster than tortoise by
= 7999.92 m/s

Question 7.
A bus is traveling at a speed of 50 km/hour. How much distance will it cover in 150 minutes?
Answer:
Speed of the bus= 50 km/h
Time taken = 150 minutes 150

\(=\frac{150}{60} \text { hours }\)

\(=\frac{15}{6} \mathrm{hr}\)

Distance = speed x time

\(=50 \times \frac{15}{6}\)
=125 km

Question 8. 
How will you make a line graph? 
Answer:
The following steps will be followed to make a graph:

1. Draw two perpendicular lines to represent the two-axis and mark them as OX and OY.
2. Showtime along X-axis and distance along the Y-axis.
3. Choose a scale to represent distance and another scale to represent the time on the graph.
4. Mark values for the time and distance on the respective scales.
5. Join all the points on the graph.

Question 9. 
What information is provided by the distance-time graph?
Answer:
The information provided by the distance-time graph is as follows :

• It tells about the distance moved by the object only at some definite time intervals.
• We can find the distance moved by the object at any instant in time.
• We can calculate the speed of the object from the distance-time graph.

Question 10. 
How will you calculate the speed of the bus from the distance-time graph?
Answer:
Find the distance corresponding to the particular time by drawing a line perpendicular to the particular time represented at point A. Note the point of intersection T with the line graph. Now draw a line parallel to X-axis intersecting the same point T which meets at point B on Y-axis. The covered distance will be OB and the time will be OA. So we can calculate speed by using the formula for the corresponding distance to the particular time.
\(=\frac{\mathrm{OB}}{\mathrm{OA}}\)

 

Question 11.
What should be the points to be kept in mind while choosing the most suitable scale for drawing a graph? 
Answer: 
The following points should be kept in mind while choosing the most suitable scale for drawing a graph :

1. The difference between the highest and the lowest values of each quantity should be known.
2. The intermediate values of each quantity should be properly visible so that it could be convenient to mark the values on the graph.
3. To utilize the maximum part of the paper on which the graph is to be drawn.

Question 12. 
Complete the data of the table given below with the help of the distance-time graph given in the figure.

Distance (m)	0	4	?	12	?	20
Time (sec)	0	2	4	?	8	10

Answer:

Distance (m)	0	4	8	12	16	20
Time (sec)	0	2	4	6	8	10