i) 90° into radian:
1⁰ = \(\frac { \pi }{ 180 } \)
90^O =\(\frac { \pi }{ 180 } \)x 90 = \(\frac { \pi }{ 2 } \)radian
ii) \(\frac { \pi }{ 6 } \) into degree
π radian = 180⁰
\(\frac { \pi }{ 6 } =\frac { 180 }{ 6 } \) = 30⁰

I = Q/t
Q= It
= 3x5
Q= 15C

1. To levitate bullet trains from the track.
2. Memory or storage element in the computer

Mole is defined as The amount of substance which contains 6.023 x 10²³ entities.

Greenwich Mean Time (GMT) :
i. The mean solar time at the Royal Observatory, located at Greenwich in London.
ii. Measured at the longitude of zero degrees.
iii. Earth is divided into 24 zones, with a width of 15 degrees longitude called Time zones.
iv. Time difference between two adjacent, time zones is 1 hour.
Indian Standard Time (1ST) :
i. The location of Mirzapur in Uttar Pradesh is taken as the reference longitude of the Indian standard time.
ii. It is located at 82.5-degree longitude.
iii. IST= GMT + 5.30 hours.

i. The result given by a calculator has too many digits.
ii. This should be rounded off to a particular digit.
iii. Rounding off is used in many areas of physics.
Rules for rounding off:
i. Decide which is the last digit to keep.
ii. Have it the same, if the next digit is less than 5.
iii. Increase it by one, if the next digit is 5 or greater than 5.

Application of Various thermometric scales:
i. Physicians use clinical thermometers graduated in Fahrenheit scale.
ii. Scientists are using thermometers with kelvin scale.
iii. Common temperature measurement are made in celsius scale.
iv. Weather reports are given in celsius scale.

Types of clocks:
I. Types of clocks based on display
(i) Analog clocks:
1. It looks like a classic clock.
2. It has three hands such as hours hand, minutes hand and seconds hand to show the time
3. Analog clocks can be driven either mechanically or electronically.
(ii) Digital clocks:
1. A digital clock displays the time directly
2. It shows the time in numerals or other symbols.
3. It may have a 12 hours or 24 hours display,
II. Types of clocks based on working mechanism
(i) Quartz clock:
1. These clocks are activated by electronic oscillations which are controlled by a 'quartz crystal'.
2. The quartz clock is more accurate than the mechanical clock.
3. Accuracy - One second in every 109 seconds.
(ii) Atomic clock:
1. These clocks are making use of periodic vibrations occurring within the atom
2. Accuracy - One second in every 10 seconds.
3. Atomic clocks are used in Global positioning System, Global Navigation Satellite System and International time distribution services.