# RBSE Solutions for Class 7 Science Chapter 11 Time and Speed

## Rajasthan Board RBSE Class 7 Science Chapter 11 Time and Speed

RBSE Solutions for Class 7 Science ### RBSE Class 7 Science Time and Speed Intext Questions and Answers

Page No 102.

Question 1.
How many hours and seconds are there in one year?

1. Hours in a year = 365 x 24 = 8760 hours
2. Seconds in a year = 365 x 24 x 60 x 60 = 31536000 seconds

Question 2.
How do we measure the time interval of one day, one month, or one year?
We measure one day in hours, one month in days and one year in months.

Page No 103.

Question 3.
We oscillate a simple pendulum for three to four times Is the periodic time for the pendulum approximately equal each time?
No, due to slight variation in initial displacement periodic time may be affected slightly.

Question 4.
What are the other big units of time?
Minutes, Hour, Day, Week, Month, Year, etc. page No 104.

Question 5.
Show by writing in following table. What is the relation between different units of time like minute, hour, day, year etc. with smaller time units?
Table: Time units and their relations. Question 6.
Let us assume that a bullock cart and motorcycle both are moving simultaneously along a straight line path. Tell which moves fast or slow?
Bullock cart is moving slow and motor cycle is moving fast.

page No 105.

Question 7.
Take the objects which move on straight line motion and pair them and then classify their speed as slow or fast in given following table in two separate columns.
Table : Slow and fast motion Question 8.
How have you ensured which object is moving slowly and which is moving fast?
When the object moves fast. then we say,that the speed of the object is more and when object moves slowly then we say that the speed is less. To know, which object is moving faster among two or more objects. the simplest method is to calculate the distance covered b the objects in unit time.

Question 9.
Following are given some pairs of moving objects. When they move simultaneously along a straight line path, then separate them in slow moving and fast moving objects –

1. Bullock cart – cycle
2. Cycle – walking man
3. Bus – Scooter
4. Aeroplane – Ship
5. Cycle – Motor cycle
6. Horse cart – Camel cart
7. Train – aeroplane.

Table : Comparative slow motion/Fast motion of objects. ### RBSE Class 7 Science Time and Speed Text Book Questions and Answers

Question 1.
If Bharti’s brother is 10 days old than his age in hours will be:
(a) 120 hours
(b) 100 hours
(c) 240 hours
(d) 80 hours
(c) 240 hours

Question 2.
The working principle of watches is based on which type of motion:
(a) Linear motion
(b) Periodic motion
(c) Curvilinear motion
(d) rotational Motion
(b) Periodic motion Question 3.
Meter per second is international unit of –
(a) Time
(b) Weight
(c) Speed
(d) Distance
(c) Speed

Fill in the blanks with suitable words:

1. The international unit of time is ………………………..
2. The distance traveled in unit time by an object is called its ………………………..
3. An object is moving with uniform speed along a straight-line. The speed of an object is called ………………………..

1. Second
2. Speed
3. Uniform motion

In the following statements, tick ‘T’ against those which are true, and ‘F’ against those which are false:

1. Each object moves in straight-line.
2. The motion of a bus is represented in meter.
3. The distance between two cities is measured in kilometre.
4. The time period for a given pendulum is not constant.
5. An object. moving with a uniform speed. has straight-line on distance – time graph

1. F
2. F
3. T
4. T
5. T Question 1.
A simple pendulum takes 80 second to complete 40 oscillations. What is the time period of the pendulum?
According to question : Number of oscillations (N) =40
Time taken for oscillations (t) = 80 seconds
Hence. Time period of pendulum (T) = $$\frac { l }{ N }$$
T = $$\frac { 80 }{ 40 }$$ second.
T = 2 seconds

Question 2.
The distance between two stations is 100 km. A bus takes 2 hours to cover this distance. Calculate the speed of the bus.
According to question : Distance between two stations = loo km, (or distance covered)
Time taken to cover the distance = 2 Hours.
Hence. speed of bus = Speed of bus = $$\frac { 100 }{ 2 }$$ km/hours
Speed of bus = 50 km/hour.

Question 3.
A motor cycle rider moves with a speed of 40 km per hour for 1.5 hour and reaches the destination. What is the total distance covered by him?
According to question: Speed = 40 km/h
Time taken in covering distance = 1.5 Hour
No distance covered by motor cycle rider = speed x time
Distance covered = 40 x 1.5
Distance covered 60 kilometre.

Question 4.
Define a solar day?
Time interval between one sun rise and the next sun rise is known as one “solar day”. Question 1.
For speed of any vehicle the distance traveled by it and the time taken is given in the table below. Draw the time distance graph. Scale: X-axis-Time, 2 seconds = 1 cm, Y-axis-Distance, 10 meter = 1cm Question 2.
What do you mean by simple pendulum? Explain its time-period.
Simple Pendulum:
The oscillation that is produced b a small metallic ball or a piece of stone suspended from rigid support by a thread is called a simple pendulum. The small metal sphere is known as ball for simple pendulum. Time period of simple pendulum:
Static simple pendulum is at rest position. It is the mean position of pendulum. When the bob of pendulum is to either side from rest position and released slowly, it begins to move to and fro. This motion is called oscillatory motion. As shown in figure. as the pendulum. starting from its mean position O. moves to A, from A to B and back from B to A is said to have completed one oscillation. Hence. Time taken by the pendulum to complete one oscillation is called periodic time of simple pendulum.

### RBSE Class 7 Science Time and Speed Important Questions and Answers

Objective Questions:

Question 1.
Period between new moon to next new moon is called a –
(a) Moon month
(b) Solar month
(c) Mal month
(d) More month
(a) Moon month

Question 2.
Clocks having electronic circuits of one or two cells are known as –
(a) Wall clock
(b) Quartz clock
(c) Hand watch
(d) None of these
(b) Quartz clock Question 3.
How symbols of units are written?
(a) In Plural form
(b) In dual form
(c) In singular form
(d) None of these
(c) In singular form

Question 4.
What is written on speedometer among the following –
(a) Km/h
(b) M/Sec
(c) Km/Sec
(d) m/h
(a) Km/h

Question 5.
The axis indicated on graph paper are –
(a) a,b
(b) A,B
(c) X,Y
(d) K,Kh
(c) X,Y

Question 6.
Where is suituated the Large Samrat clock’?
(a) Udaipur
(b) Ajmer
(c) Jodhpur
(d) Jaipur
(d) Jaipur

Question 7.
Distance covered by an object in unit time is known as objects –
(a) Force
(b) Time
(c) pressure
(d) speed
(d) speed

Question 8.
The distance and time are written on speedometer of any vehicle in –
(a) M/h
(b) M/sec
(c) Km/h
(d) Km/sec
(c) Km/h Question 9.
Periodic events are used in measurement of –
(a) Time
(b) Distance
(c) Speed
(d) Force
(a) Time

Fill in the blanks:

1. Sphere of metal is known as ball of …………………. (Simple pendulum / oscillation)
2. Clocks work based on …………………. (Simple motion / Periodic motion)
3. Time interval between one sunrise and the next sunrise is known as …………………. (solar day / solar time)
4. Our ancestors made …………………. as a base to measure time. (Linear motion / Periodic motion)
5. Meter per second is the international unit of …………………. (time / speed)

1. Simple pendulum
2. Periodic motion
3. Solor day
4. Periodic motion
5. Speed.

Match the column I with column II

Question 1. 1. (b)
2. (a)
3. (d)
4. (e)
5. (c)

Question 1.
Where ‘Jantar Mantar’ is situated in Rajasthan?
It is in Jaipur.

Question 2.
What is moon month?
Period between new moon to next new moon is called as one “moon-month’.

Question 3.
What is a year?
Time interval in which earth completes one rotation around sun, is known as year.

Question 4.
Name the measurement methods used to measure time in ancient time.

1. Sand clock
2. Water clock

Question 5.
Which motion is found in simple pendualum?
Periodic motion or oscillation motion. Question 6.
What is ball of a simple pendulum?
The small metal sphere is known as ball for simple pendulum.

Question 7.
What is known as oscillatory motion?
The to and fro motion of simple pendulum is known as oscillatory motion.

Question 8.
What is time period?
Time taken by the pendulum to complete one oscillation is called period time of simple pendulum.

Question 9.
What is required for measurement of time period of an simple pendulum?
Stop watch is required

Question 10.
Does slight variation in initial displacement affect the period time of a pendulum?
Does not affect.

Question 11.
What is the international unit of time?
Second is the International unit of time.

Question 12.
What is the smallest unit of time?
Second

Question 13.
What is the pulse rate of a normal healthy man at rest?
Around 72 times in one minute.

Question 14.
Write some big units of time.
Minutes, hour, day, week, month, year etc.

Question 15.
How do we compare the motion of two objects as slow or fast motion?
By comparing speeds of both the objects.

Question 16.
What is known as speed?
Speed is the distance covered by an object in unit time. Question 17.
Can a vehicle move with a constant speed?
No, it depends on state of path used.

Question 18.
What is international unit of speed?
Meter per second.

Question 19.
What are the various units of speed?
Centimetre/second, Km/sec, Km/hour.

Question 20.
What do you mean by nano second?
It is the one trillionth part of second.

Question 21.
What is micro second?
It is ten millionth fraction of a second.

Question 22.
State the formulae to find out the speed of an object.
Speed Question 23.
Write formulae to calculate the distance covered by an object?
Distance covered = speed x time

Question 24.
Write formulae to calculate the time consumed to cover a distance.
Time taken to cover a particular distance Question 1.
State the events by which we come to know about time and time intervals.
Many periodic events occur in nature which happens repeatedly after specific time intervals by which c come to know about time and time intervals. These are

1. Solar day – Time interval between one sun rise and next sunrise is known as one solar day”.
2. Moon month – Period between new moon to next new moon is called as one moon-month.
3. Year – The time at which earth completes one revolution around the sun has been fixed as one car time period.

Question 2.
What is ‘Large samrat clock”. Where it is situated? Who built it?
At capital city Jaipur of Rajasthan. we have a – Large Samrat clock” sun clock at Jantar-Manter which measures even 2 secs with accuracy, it was built in 1735 AD by Maharaja Swai Jai Singh. Question 3.
How different units of time are used?
In following way the different units of time are used/implemented’?

1. Second – We use this unit in measuring time at micro level.
2. Minute – It is used to measure time above the micro level.
3. Hour – For duration of long time in a day.
4. Day – For time greater than 24 hours.
5. Month – For approx time greater than 30 days.
6. Year – For duration of time greater than twelve months. According to necessity. the different units of time can be used.

Question 4.
What are the characteristics of clocks present in India’s National physical laboratory, new delhi”
India’s National Physical Laboratory. New Delhi prov ides time maintenance service. The clocks arc available here can measure of ten millionth of one second with accuracy.

Question 5.
Differentiate between uniform speed and un uniform speed. Question 6.
Write formulae of average speed of an object, distance covered and time taken to cover the distance.
1. Speed 2. Distance covered = Speed x Time

3. Time taken to cover the distance Question 7.
State in short about following. Draw diagram also.

1. Speedometer
2. Odometer

1. Speedometer You may have seen a meter in motorcycle, car, bus or other vehicle as shown in figure. Km/h is written on the meter. It is known as speedometer’. By this, speed can be measured directly in Km/h. Kilometres are indicated on it.
2. Odometer – There is another meter in vehicles which measures the distance traveled by a vehicle. It is called odometer. Question 8.
How it is found out that an object is moving with uniform speed or non uniform speed by distance-time graph?
If the distance-time graph is straight-line. it indicates that the object is moving with a constant speed. If speed of an object keeps on changing, the nature of graph will be different.

Question 9.
State the name of five objects moving along a straight path.
Name of objects moving along a straight – line path –

1. Camel cart moving on straight road.
2. Bus running on straight road.
3. Soldiers doing march past.
4. Train running on straight track
5. Motor cycle moving on straight road. Question 10.
What is difference between modern watch and ancient watch? Draw a diagram of a digital clock.
1. Ancient watches –
It was not possible to measure time at micro level by using ancient watches. Also these watches were less significant for scientific researches and were less useful in measuring time for micro level.

2. Modern watches –
Now a days. quartz watches. digital watches are available whose measurement is more accurate. Excepts these. today specific clocks are available for use in scientific research. Among them few are able to measure ten millionth fraction of one second (micro second) and also one trillionth part of a second (nano second). Question 11.
State different units of speed. Also tell how they are written.
The international unit of speed is meter per second. The other units of speed arc as follows –

1. Centimeter per second (cm/s)
2. Kilometer per second (Km/s)
3. Kilometer per hour (Km/h) etc.

You must remember that all the symbols of units are written in singular person. For example – For distance we write 80 Km, not 80 Kms. Question 12.
Calculate number of seconds in one day.
We know that
1 day = 24 Hours
1 Hours =60 Minute
1 Minute = 60 Second
Thus, 1 hour contains 3600 second (60 x 60) and in 24 hour – 24 x 3600 second so. 86400 second
Hence. 1 day (24 Hours) contain 86400 second

Essay Type Questions:

Question 1.
Following are given the time and distance values for a moving car. Draw a distance-time graph by using these values. Scale : on X – axis: time
5 second = 1 cm
On Y – axis : Distance – 10 meter = 1 cm Question 2.
Write the steps for making a graph between distance and time on graph paper. Steps for making a graph:

1. To represent two axes, draw two perpendicular lines and mark OX and OY on it as shown in figure.
2. Represent time on x-axis and distance on Y-axis.
3. Choose an appropriate scale to represent the distance along Y-axis and time on x axis.
4. As per scale selection, mark values for time and distance on X-axis and Y-axis respectively.
5. Mark other points of different sets values on the graph paper.
6. Mark all the different sets of time and distance covered by the car on graph paper.
7. Join all these points on the graph. You will find a straight line after joining the points This is the time-distance graph for speed of car.

Question 3.
Distance from Jaipur to Udaipur is 440 Km. A car takes total 8 hours time to cover this distance. Calculate the speed of car in kilometre per hour.
According to question – distance from Jaipur to Udaipur = 440 Km Time taken by the car to cover this
distance = 8 Hours Hence,
speed of car = $$\frac { 440 }{ 8 }$$ Km per hour
Speed of car = 55 Km per hour. Question 4.
Ishan reached to his sister’s house by the speed of 50 kilometre/hour in 2.5 hours by his motorcycle. Calculate the distance covered by Ishan.
According to question: Speed 50 km per hour Time taken to cover the distance = 2.5 Hour
Hence, distance covered by Ishan = 50 x 2.5 Km = 125 Kilometre.

Question 5.
An vehicle starts at 6:00 in the morning from a place. For motion of this vehicle, distance covered and time values are given in the following table. Prepare a distance-time graph according to these values. Scale: On X-axis:
Time – half hour = 1 cm
One Y-axis:
Distance – 20 Km = 1 cm Question 6.
The distance from a initial point of a car and odometer reading during 30 minutes interval are as follows – Based on above table find out –

1. How much distance was covered by the car?
2. What is the average speed of the car?
3. How much distance has been covered on 9:00 am by the car?
4. When was car at 120 Km distance? $$\frac { 60 }{ 2 }$$ = 80 kilometre/hour