##### Class 10^{th} Science Tamilnadu Board Solution

**Part-a**- Screw Gauge is an instrument used to measure the dimensions of very small objects upto…
- In a Screw Gauge, if the zero of the head scale lies below the pitch scale axis, the zero…
- The Screw Gauge is used to measure the diameter of a _________ (crowbar, thin wire,…
- One light year is equal to _________.i) 365.25 x 24 x 60 x 60 x 3 x 108 mii) 1x 24 x 60 x…
- One astronomical unit is the mean distance between the centre of the Earth and centre of…

**Part-b**- Correct the mistakes if any, in the following statements:i) Astronomical unit is the mean…
- Match the items in group A with the items in group B:Sl.No.Group – AGroup – B1.Small…
- Fill in the blanks:The special methods adopted to determine very large distances are…
- Least count of a screw gauge is an important concept related to screw gauge. What do you…
- Label the following parts in the given screw gauge diagram.i) Head scale ii) Pitch…

**Part-a**

- Screw Gauge is an instrument used to measure the dimensions of very small objects upto…
- In a Screw Gauge, if the zero of the head scale lies below the pitch scale axis, the zero…
- The Screw Gauge is used to measure the diameter of a _________ (crowbar, thin wire,…
- One light year is equal to _________.i) 365.25 x 24 x 60 x 60 x 3 x 108 mii) 1x 24 x 60 x…
- One astronomical unit is the mean distance between the centre of the Earth and centre of…

**Part-b**

- Correct the mistakes if any, in the following statements:i) Astronomical unit is the mean…
- Match the items in group A with the items in group B:Sl.No.Group – AGroup – B1.Small…
- Fill in the blanks:The special methods adopted to determine very large distances are…
- Least count of a screw gauge is an important concept related to screw gauge. What do you…
- Label the following parts in the given screw gauge diagram.i) Head scale ii) Pitch…

###### Part-a

**Question 1.**Screw Gauge is an instrument used to measure the dimensions of very small objects upto _________ (0.1 cm, 0.01 cm, 0.1 mm, 0.01 mm)

**Answer:**0.01 mm

__Explanation:__The least count of screw gauge is given by;

Where pitch is the distance moved on the linear scale of the screw gauge in one rotation.

**Question 2.**In a Screw Gauge, if the zero of the head scale lies below the pitch scale axis, the zero error is_________ .(positive, negative, nil)

**Answer:**The zero error in this case is positive.

__Explanation:__ In a Screw Gauge, if the zero of the head scale lies below the pitch scale axis, the zero error is positive by convention and it’s then subtracted from the final measured value. If the zero of the head scale lies below the pitch scale axis, the zero error is considered negative and it’s then added to the final measured value.

**Question 3.**The Screw Gauge is used to measure the diameter of a _________ (crowbar, thin wire, cricket ball )

**Answer:**Thin wire.

__Explanation:__ A screw gauge is used for measuring very small diameters of the order of 0.01 mm. So it’s suitable only for measuring the diameter of a thin wire.

**Question 4.**One light year is equal to _________.

i) 365.25 x 24 x 60 x 60 x 3 x 10^{8} m

ii) 1x 24 x 60 x 60 x 3 x 10^{8} m

iii) 360 x 24 x 60 x 60 x 3 x 10^{8} m

**Answer:**(iii) is correct.

__Explanation:__ A light year is the distance traversed by light in one year. So it is given by

Speed of light × No. of seconds in a year=

365.25 x 24 x 60 x 60 x 3 x 10^{8} m

The no. of seconds in a year is given by the no. of days in a year ×no. of hours in a day × no. of minutes in an hour× no. of seconds in a minute.

**Question 5.**One astronomical unit is the mean distance between the centre of the Earth and centre of the _________ i) Moon ii) Sun iii) Mars

**Answer:**(ii)is correct.

__Explanation:__ An astronomical unit is defined as the distance between the centre of the Earth and the centre of the Sun.

**Question 1.**

Screw Gauge is an instrument used to measure the dimensions of very small objects upto _________ (0.1 cm, 0.01 cm, 0.1 mm, 0.01 mm)

**Answer:**

0.01 mm

** Explanation:**The least count of screw gauge is given by;

Where pitch is the distance moved on the linear scale of the screw gauge in one rotation.

**Question 2.**

In a Screw Gauge, if the zero of the head scale lies below the pitch scale axis, the zero error is_________ .(positive, negative, nil)

**Answer:**

The zero error in this case is positive.

** Explanation:** In a Screw Gauge, if the zero of the head scale lies below the pitch scale axis, the zero error is positive by convention and it’s then subtracted from the final measured value. If the zero of the head scale lies below the pitch scale axis, the zero error is considered negative and it’s then added to the final measured value.

**Question 3.**

The Screw Gauge is used to measure the diameter of a _________ (crowbar, thin wire, cricket ball )

**Answer:**

Thin wire.

** Explanation:** A screw gauge is used for measuring very small diameters of the order of 0.01 mm. So it’s suitable only for measuring the diameter of a thin wire.

**Question 4.**

One light year is equal to _________.

i) 365.25 x 24 x 60 x 60 x 3 x 10^{8} m

ii) 1x 24 x 60 x 60 x 3 x 10^{8} m

iii) 360 x 24 x 60 x 60 x 3 x 10^{8} m

**Answer:**

(iii) is correct.

** Explanation:** A light year is the distance traversed by light in one year. So it is given by

Speed of light × No. of seconds in a year=

365.25 x 24 x 60 x 60 x 3 x 10^{8} m

The no. of seconds in a year is given by the no. of days in a year ×no. of hours in a day × no. of minutes in an hour× no. of seconds in a minute.

**Question 5.**

One astronomical unit is the mean distance between the centre of the Earth and centre of the _________ i) Moon ii) Sun iii) Mars

**Answer:**

(ii)is correct.

** Explanation:** An astronomical unit is defined as the distance between the centre of the Earth and the centre of the Sun.

###### Part-b

**Question 1.**Correct the mistakes if any, in the following statements:

i) Astronomical unit is the mean distance of the surface of the sun from the surface of the earth.

ii) Light year is the distance travelled by light in one year in vacuum at a speed of 3x10^{8}m per minute.

**Answer:**(i) False.

__Explaantion:__ An astronomical unit is defined as the distance between the __centre__ of the Earth and the __centre__ of the Sun.

ii) False.

__Explanation:__ Light year is the distance travelled by light in one year in vacuum at a speed of 3x10^{8}m per __second__.

**Question 2.**Match the items in group A with the items in group B:

**Answer:**1. Small dimensions- Screw gauge, Scale

2. Large dimensions-Altimeter

3. Long distance – Light year

4. Small distance-Kilometre

**Question 3.**Fill in the blanks:

The special methods adopted to determine very large distances are _________and (Laser pulse method, Light year method, Radio echo method, Astronomical method)

**Answer:**Radio echo method, Laser pulse method.

__Explanation:__ Radio echo method using three receivers spaced on the ground by 4 km has been used to determine the orbits of individual meteors.

In laser pulse method, a laser pulse is reflected from the object frim which distance is to be measured. The time taken is measured and using the speed of light, the distance is calculated.

**Question 4.**Least count of a screw gauge is an important concept related to screw gauge. What do you mean by the term least count of a screw gauge?

**Answer:**The least count of screw gauge is given by;

Where pitch is the distance moved on the linear scale of the screw gauge in one rotation.

**Question 5.**Label the following parts in the given screw gauge diagram.

i) Head scale ii) Pitch scale

iii) Index line iv) Ratchet

**Answer:**

**Question 1.**

Correct the mistakes if any, in the following statements:

i) Astronomical unit is the mean distance of the surface of the sun from the surface of the earth.

ii) Light year is the distance travelled by light in one year in vacuum at a speed of 3x10^{8}m per minute.

**Answer:**

(i) False.

** Explaantion:** An astronomical unit is defined as the distance between the

__centre__of the Earth and the

__centre__of the Sun.

ii) False.

** Explanation:** Light year is the distance travelled by light in one year in vacuum at a speed of 3x10

^{8}m per

__second__.

**Question 2.**

Match the items in group A with the items in group B:

**Answer:**

1. Small dimensions- Screw gauge, Scale

2. Large dimensions-Altimeter

3. Long distance – Light year

4. Small distance-Kilometre

**Question 3.**

Fill in the blanks:

The special methods adopted to determine very large distances are _________and (Laser pulse method, Light year method, Radio echo method, Astronomical method)

**Answer:**

Radio echo method, Laser pulse method.

** Explanation:** Radio echo method using three receivers spaced on the ground by 4 km has been used to determine the orbits of individual meteors.

In laser pulse method, a laser pulse is reflected from the object frim which distance is to be measured. The time taken is measured and using the speed of light, the distance is calculated.

**Question 4.**

Least count of a screw gauge is an important concept related to screw gauge. What do you mean by the term least count of a screw gauge?

**Answer:**

The least count of screw gauge is given by;

Where pitch is the distance moved on the linear scale of the screw gauge in one rotation.

**Question 5.**

Label the following parts in the given screw gauge diagram.

i) Head scale ii) Pitch scale

iii) Index line iv) Ratchet

**Answer:**