RBSE Solutions for Class 7 Science Chapter 11 Time and Speed

RBSE Solutions for Class 7 Science Chapter 11 Time and Speed are part of RBSE Solutions for Class 7 Science. Here we have given Rajasthan Board RBSE Class 7 Science Chapter 11 Time and Speed.

Board	RBSE
Textbook	SIERT, Rajasthan
Class	Class 7
Subject	Science
Chapter	Chapter 11
Chapter Name	Time and Speed
Number of Questions Solved	50
Category	RBSE Solutions

Rajasthan Board RBSE Class 7 Science Chapter 11 Time and Speed

Text book Exercise

Multiple Choice Questions :

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

Question 3.
Meter per second is International unit of:
(a) Time
(b) Weight
(c) Speed
(d) Distance
Answer:
(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 it’s …………………
3. An object is moving with uniform speed along a straight-line. The speed of an object is called …………
Answer:

1. Second
2. Speed
3. Uniform or constant speed

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. (T/F)
2. The motion of a bus is represented in meter. (T/F)
3. The distance between two cities is measured in kilometer. (T/F)
4. The time period for given pendulum is not constant. (T/F)
5. An object, moving with a uniform speed, has straight-line on distance-time graph. (T/F)
Answer:

1. False
2. False
3. True
4. False
5. True

Short Answer Type Questions

Question 1.
A simple pendulum takes 80 seconds to complete 40 oscillations. What is the time period of the pendulum?
Answer:
Time period of pendulum=t / N = 80/40 = 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.
Ans:
Speed=distance / time
distance 100 km Time taken 2 hours Speed =100 km / 2 hours = 50 km / h

Question 3.
A motorcycle rider moves with a speed of 40 km/h for 1.5 hours and reaches the destination. What is the total distance covered by him?
Answer:
Speed of motorcycle = 40 km/hr
Time taken = 1.5 hrs
Distance travelled=speed x distance
= 40 x 1.5 km =60 km

Question 4.
Define a solar day?
Answer:
Sun rises in morning every day. Time intervals between one sun rise and the next sun rise is known as one “Solar-day”.

Long Answer Type Questions:

Question 1.
For speed of any vehicle the distance travelled by it and the time taken is given in the table below. Draw the time-distance graph.

S.No.	Time	Distance
1	2 minutes	10m
2	4 minutes	20m
3	6 minutes	30km
4	8 minutes	40km
5	10 minutes	50km

Answer:

Question 2.
What do you mean by simple pendulum? Explain its time-period.
Answer:
The oscillation that is produced by a small metallic ball or a piece of stone suspended from rigid support by a thread is called a simple pendulum. Time taken by the pendulum to complete one oscillation is called periodic table of simple pendulum.

Activity
Question 1.
Observe the speed of your nearby objects on the earth, in air and water. By observing the distance travelled and time taken, find out the speed of these objects.
1. Speed of boat in water
If distance travelled by boat in 10 min is 600 m
Then speed of boat = 600/10 = 60 m/min
2. Speed of car
If distance travelled by car in 1 hour is 80 km
Then speed of car = 80/lk = 80 km/h
3. Speed of bird
If distance travelled by a bird in 30 sec is 90 m
Then speed of bird = 90/30 = 3 m/sec
4. Take two plastic bottles.
Fill sand in one bottle, cap the bottle and make a hole into the cap.
Fit another plastic bottle on it without cap and make a model of sand watch.
Answer:
Students should do themselves.

In Text Questions

Question 1.
If you do not have watch then how will you decide what is the time right now?(Page 101)
Answer:
We can estimate the time by the position of the Sun and its shadow.

Question 2.
Are you not eager to know that how our ancestors could tell the approximate time of the day by just looking at shadow? (page-101)
Answer:
Yes, some old people estimate the time by fixing stick and measuring its shadow with fingers.

Question 3.
Find out how many hours and seconds are there in 1 year. (page 102)
Answer:
Hours in one year = 365 x 24 (24 hours of day and night)
= 8760 hours
Seconds in a year = 8760 x 60 x 60 (60 minutes in one hour and 60 seconds in one minute)
=3,15,36,000 seconds

Question 4.
The time interval of one second is how much short or long? (page 103)
Answer:
The pronunciation of two or three words loudly like” Jai Rajasthan”takes approximately one second by us. At rest, the pulse rate of a normal healthy man is 72 times in one minute i. e., 12 times in 10 second. In children, it can be slightly increased.

Question 5.
What are the other big units of time? Show by writing in table, what is the relation between different units of time like minute, hour, day, year etc. with smaller time units ? (Page 103-104)
Answer:

S.No.	Unit Name	Relation with small unit
1	Minute	1 Minute = 60 Seconds
2	Hour	1 Hour =60 Minutes = 3600 Seconds
3	Day	1 Day = 24 Hours = 1440 Minutes
4	Year	1 Year = 365 Day = 8760 Hours

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? (page 104)
Answer:
The speed of motor cycle is fast and that of bullock cart is slow.

Question 7.
Similarly take the objects which move on straight line motion and pair them and then classify their speed as slow or fast in table in two separate columns. (Page 105).
Answer:

S. No.	Pair of objects	Slow motion	Fast motion
1	Car and Motorcylce	car	M. Cycle
2	Pedestrian or cycler	pedestrian	cycler
3	Truck and train	truck	train
4	Tortoise and rabbit	tortoise	Rabbit
5	ship and aeroplane	ship	aeroplane
6	cycle and scooter	cycle	scooter
7	boat and steamer	boat	steamer
8	horse-cart and came 1 cart.	camel cart	horse cart

Question 8.
How have you ensured which object is moving slowly and which is moving fast? (page 105)
Answer:
It can be estimated by comparing distance from a fixed point which object is moving fast and which is slow.

Other Important Questions

Multiple Choice Questions :

Question 1.
Where is” Large Samrat Clock” situated?
(a) Udaipur
(b) Jaipur
(c) Jodhpur
(d) Bikaner
Answer:
(b) Jaipur

Question 2.
The number of seconds in one minute is:
(a) 60
(b) 120
(c) 900
(d) 600
Answer:
(a) 60

Question 3.
The unit of speed is:
(a) m/sec
(b) km/h
(c) cm/sec
(d) all the above
Answer:
(d) all the above

Question 4.
Device used to measure distance is:
(a) speedometer
(b) Odometer
(c) Thermometer
(d) cubic meter
Answer:
(b) Odometer

Question 5.
The correct way of writing unit of distance is:
(a) h/s
(b) ms
(c)km
(d) All these
Answer:
(c)km

Question 6.
The unit of time is
(a) second
(b) minute
(c) hour
(d) All these
Answer:
(d) All these

Question 7.
The motion of pendulum of clock is:
(a) periodic motion
(b) Linear motion
(c) circular motion
(d) rotational motion
Answer:
(a) periodic motion

Fill in the blanks:
1. In ancient times,…….watch and………..watch were used to calculate time.
2. The time period between two new moon day is called …………..
3. The metal ball is known as ……….. of simple pendulum.
4. ………….is the international unit of speed.
5. The distance time graph for uniform speed is s ………….
Answer:

1. Sand ,sun-light
2. lunar month
3. ball
4. Metre/ second
5. straight line

Very Answer Type Questions:

Question 1.
How much time can be purely measured by solar clock situated at Jaipur?
Answer:
Small time upto 2 seconds can be measured.

Question 2.
By whom and when was Large Samrat clock built?
Answer:
Large Samrat clock was built by Maharaja of Jaipur, Swai Jai Singh in 1735 AD.

Question 3.
What is lunar month?
Answer:
The time period between two new moon day is called Lunar month.

Question 4.
What is a year?
Answer:
The time taken by the earth to make one revolution around the sun is considered as one year.

Question 5.
Write the formula to calculate speed of an object.
Answer:
Speed = distance / time.

Question 6.
Write the formula used to measure distance travelled by an object?
Answer:
Distance = speed x time

Question 7.
Write the formula used to measure time taken by an object to cover a distance ?
Answer:
Time = distance / speed

Short Answer Type Questions:

Question 1.
Calculate seconds in a day.
Answer:
If mean solar day is assumed as standard time and it is divided into 24 equal parts then 1 day = 24 hours.
Similarly, if one hour is divided into 60 equal minutes and one minutes is divided into 60 equal seconds, then
1 hour=60 minutes
1 minute = 60 seconds
Similarly, you will find that 1 hour has 3600 seconds and 1 day has 86400 seconds.

Question 2.
Describe different types of watch?
Answer:
Now a days, most of clocks have electronic circuits of one or two cells. These clocks are called quartz clocks. The time measured by these watches is more accurate as compared to earlier watches. In addition, today the electronics or digital clocks are also available in which time
is expressed in digits.

Question 3.
Write different units of speed. How are they used?
Answer:
The international unit (SI) of speed is meter per second. The other units of speed are centimeter per second (cm/s), kilometer per second (km/s), kilometer per hour (km/h), etc. you must remember that all symbols of units are written in singular number. For example, for distance we write 50 km, but not 50 kms or 8 cm but not 8 cms.

Long Answer Type Questions:

Question 1.
Define uniform and average speed.
Answer:
If the speed of an object along a straight line path keeps on changing,then it is called non uniform speed of that object. When we say that a car has speed of 50 km per hour, usually we only consider the distance travelled by a car in one hour. We do not bother about the speed of car as uniform or non-uniform in one hour. In reality, the calculated speed is the average speed of a car. When an object moves along on straight line with constant speed then it is known as constant speed or uniform speed. In this condition of uniform speed, the average speed is equal to its actual speed. The calculation of speed is done by dividing the total distance covered by the object by total time taken.

Question 2.
Discuss in short time calculation in ancient time. Define abstract and real time.
Answer:
In India, there has been a tradition to measure smallest time unit since ancient times. It is evidenced in many books which explain in detail about time calculation. There is no evidence for this time calculation in any other civilisation of the world. As described in Sun Theory book time has two forms.
Abstract time: ” It is the time which can neither be seen nor calculated by the simple methods.This type of time cannot be perceived by ordinary sense organs”. Real time:” This time can be Calculated and can be visualised and felt”.

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