Selina solutions concise physics class 9 icse Solutions for Chapter 1 chapter 1 measurements and experimentation

What do you understand by the term unit?

What are the three requirements for selecting a unit of a physical quantity?

Name the three systems of unit and state the various fundamental units in them.

Define a fundamental unit.

Explain the meaning of derived unit with the help of one example.

Write the name of two units of length smaller than a metre. How are they related to the metre?

How is nanometer related to Angstrom?

Name the three convenient units used to measure length ranging from very short to very long value. How are they related to the S.I. unit?

Name the S.I unit of mass and define it.

Complete the following:

(a) 1 light year = ________ m

(b) 1 m = ________ Å

(c) 1 m = ________ µ

(d) 1 micron = ________ Å

(e) 1 fermi = ________ m

State two units of mass smaller than a kilogram. How are they related to kilogram?

Name the S.I. unit of time and define it.

Name two units of time bigger than a second. How are they related to second?

What is a lunar month?

Complete the following:

(a) 1 nano second = ________s

(b) 1 µs = _______s

(c) 1 mean solar day = ________s

(d) 1 year = ________s

Write the derived units of the following:

(a) Speed

(b) Force

(c) Work

(d) Pressure

Name the physical quantities related to the following units:

(a) km2

(b) newton

(c) joule

(d) pascal

(e) watt

The unit of time is:

(a) light year

(b) parsec

(c) leap year

(d) angstrom

1 Å is equal to:

(a) 0.1 nm

(b) 10^{-10} cm

(c) 10^{-8} m

(d) 10^4 µ

ly is the unit of:

(a) time

(b) length

(c) mass

(d) none of these

The wavelength of light of a particular colour is 5800 Å. Express it in (a) nanometer and (b) metre

The size of a bacteria is 1 µ. Find the number of bacteria in 1m length.

The mass of an oxygen atom is 16.00 u. Find its mass in kg.

It takes time 8 min for light to reach from the sun to the earth surface. If speed of light is taken to be 3 \times 10^8 ms^{-1}, find the distance from the sun to the earth in km.

‘The distance of a star from the earth is 8.33 light minutes’. What do you mean by this statement? Express the distance in the metre.

A boy makes a ruler with graduation in cm on it (i.e., 100 divisions in 1m). To what accuracy this ruler can measure? How can this accuracy be increased?

A vernier callipers have a zero error +0.06cm. Draw a neat labelled diagram to represent it.

State three uses of vernier calipers.

Name the two scales of a vernier callipers and explain, how it is used to measure a length correct up to 0.01cm.

Describe in steps, how would you use a vernier calliper to measure the length of a small rod?

Explain the terms (i) pitch, and (ii) least count of a screw gauge. How are they determined?

Draw a neat labelled diagram of a screw gauge. Name its main parts and state their functions.

State the purpose of ratchet in a screw gauge.

What is backlash error? Why is it caused? How is it avoided?

Name the instrument which can measure accurately the following:

(a) The diameter of a needle

(b) The thickness of a paper

(c) The internal diameter of the neck of a water bottle

(d) The diameter of a pencil

Name the instrument which has the least count:

(a) 0.1mm

(b) 1mm

(c) 0.01mm

The least count of a vernier calipers is:

(a) 1cm

(b) 0.001cm

(c) 0.1cm

(d) 0.01cm

A microscope has its main scale with 20 divisions in 1cm and vernier scale with 25 divisions, the length of which is equal to the length of 24 divisions of main scale. The least count of microscope is:

(a) 0.002cm

(b) 0.001cm

(c) 0.02cm

(d) 0.01cm

The diameter of thin wire can be measured by:

(a) A vernier callipers

(b) A metre rule

(c) A screw gauge

(d) None of these

A stopwatch has 10 divisions graduated between the 0 and 5s marks. What is its least count?

A vernier has 10 divisions and they are equal to 9 divisions of the main scale in length. If the main scale is calibrated in mm, what is its least count?

A boy uses vernier callipers to measure the thickness of his pencil. He measures it to be 1.4mm. If the zero error of vernier callipers is +0.02cm, what is the correct thickness of pencil?

A vernier calliper has its main scale graduated in mm and 10 divisions on its vernier scale are equal in length to 9mm. When the two jaws are in contact, the zero of vernier scale is ahead of zero of the main scale and 3rd division of vernier scale coincides with the main scale division. Find: (i) the least count and (ii) the zero error of the vernier callipers.

The main scale of vernier callipers is calibrated in mm and 19 divisions of the main scale are equal in length to 20 divisions of the vernier scale. In measuring the diameter of a cylinder by this instrument, the main scale reads 35 divisions and 4th division of vernier scale coincides with the main scale division. Find: (i) least count and (ii) radius of a cylinder.

In vernier callipers, there are 10 divisions on the vernier scale and 1cm on the main scale is divided into 10 parts. While measuring a length, the zero of the vernier lies just ahead of 1.8cm mark and 4th division of vernier coincides with a main scale division.

(a) Find the length

(b) If zero of vernier callipers is -0.02cm, what is the correct length?

While measuring the length of a rod with vernier callipers, Figure below shows the position of its scales. What is the length of the rod?

The pitch of a screw gauge is 0.5mm and the head scale is divided into 100 parts. What is the least count of screw gauge?

The thimble of a screw gauge has 50 divisions. The spindle advances 1mm when the screw is turned through two revolutions.

(i) What is the pitch of screw gauge?

(ii) What is the least count of the screw gauge?

The pitch of a screw gauge is 1mm and its circular scale has 100 divisions. In the measurement of the diameter of a wire, the main scale reads 2mm and 45th mark on circular scale coincides with the baseline. Find:

(i) The least count, and

(ii) The diameter of the wire

When a screw gauge of least count 0.01mm is used to measure the diameter of a wire, the reading on the sleeve is found to be 1mm and the reading on the thimble is found to be 27 divisions. (i) what is the diameter of the wire in cm? (ii) if the zero error is +0.005cm, what is the correct diameter?

A screw gauge has 50 divisions on its circular scale and its screw moves by 1mm on turning it by two rotations. When the flat end of the screw is in contact with the stud, the zero of circular scale lies below the base line and 4th division of circular scale is in line with the base line. Find: (i) the pitch, (ii) the least count and (iii) the zero error, of the screw gauge.

The figure below shows the reading obtained while measuring the diameter of a wire with a screw gauge. The screw advances by 1 division on the main scale when the circular head is rotated once.

Find (i) pitch of the screw gauge,

(ii) Least count of the screw gauge, and

(iii) The diameter of the wire.

A screw has a pitch equal to 0.5mm. What should be the number of division on its head so as to read correct up to 0.001mm with its help?

What is a simple pendulum? Is the pendulum used in a pendulum clock simple pendulum? Give a reason for your answer.

Define the terms: (i) oscillation, (ii) amplitude (iii) frequency (iv) time period as related to a simple pendulum

Draw a neat diagram of a simple pendulum. Show on it the effective length of the pendulum and its one oscillation.

Name two factors on which the time period of a simple pendulum depends. Write the relation for the time period in terms of the above-named factors.

Name two factors on which the time period of a simple pendulum does not spend.

How is the time period of a simple pendulum affected, if at all, in the following situations:

(a) The length is made four times,

(b) The acceleration due to gravity is reduced to one-fourth.

How is the time period T and frequency f of an oscillation of a simple pendulum related?

How do you measure the time period of a given pendulum? Why do you note the time for more than one oscillation?

How does the time period (T) of a simple pendulum depend on its length (l)? Draw a graph showing the variation of T2 with l. How will you use this graph to determine the value of g (acceleration due to gravity)?

Two simple pendulum A and B have equal lengths, but heir bobs weigh 50 gf and 100 gf respectively. What would be the ratio of their time periods? Give reason for your answer.

Two simple pendulums A and B have lengths 1.0m and 4.0m respectively at a certain place. Which pendulum will make more oscillations in 1 minute? Explain your answer.

State how does the time period of a simple pendulum depend on (a) length of the pendulum, (b) mass of bob, (c) amplitude of oscillation and (d) acceleration due to gravity.

What is a seconds’ pendulum?

State the numerical value of the frequency of oscillation of a seconds’ pendulum. Does it depend on the amplitude of oscillation?

The length of a simple pendulum is made one-fourth. Its time period becomes:

(a) Four times

(b) One-fourth

(c) Double

(d) Half

The time period of a simple pendulum is 2s. What is its frequency? What name is given to such a pendulum?

The time period of a pendulum clock is:

(a) 1s

(b) 2s

(c) 1 min

(d) 12h

The length of a seconds’ pendulum is nearly:

(a) 0.5m

(b) 9.8m

(c) 1.0m

(d) 2.0m

A simple pendulum completes 40 oscillations in one minute. Find its (a) frequency, (b) time period.

A seconds’ pendulum is taken to a place where the acceleration due to gravity falls to one-fourth. How is the time period of the pendulum affected, if at all? Give reason. What will be its new time period?

Find the length of a seconds’ pendulum at a place where g=10ms^{-1} (Take π =3.14).

Compare the time periods of two pendulums of length 1m and 9m.

A Pendulum completes 2 oscillations in 5s.

(a) What is its time period?

(b) If g=9.8 ms-2, find its length.

The time periods of two simple pendulums at a place are in the ratio 2:1. What will be the ratio of their lengths?

It takes 0.2s for a pendulum bob to move from mean position to one end. What is the time period of the pendulum?

How much time does the bob of a seconds’ pendulum take to move from one extreme of its oscillation to the other extreme?