## Measurements and Experiments

**Q1. Define physical quantity. Give examples.**

Ans: The type of quantity that can be measured is called a physical quantity. Example: length, time, mass etc.

**Q2. Name the three systems of the unit and state their various fundamental units.**

Ans: Three systems of unit and their fundamental units:

a) **M.K.S. system:** In this system, the unit of length is meter (m), unit of mass is kilogram (kg) and unit of time is second (s).

b) **C.G.S. system:** In this system, the unit of length is centimeter (cm), unit of mass is gram (g) and unit of time is second (s).

c) **F.P.S. system:** In this system, the unit of length is foot (ft), unit of mass is pound (lb) and unit of time is second (s).

**Q3. Name two units of length that are bigger than a meter.**

Ans: Astronomical unit (A.U.) and kilometre (km)

**Q4. How is nanometre related to Angstrom?**

Ans: one nanometer is equal to ten times of an angstrom ie 1 nm = 10 Å

**Q5. State two units of mass bigger than a kilogram. Give their relationship with the unit kilogram.**

Ans: The units ‘quintal’ and ‘metric tonne’ are two units of mass bigger than ‘kilogram’.

1 quintal = 100 kg

1 metric tonne = 1000 kg

**Q6. ‘The year 2024 will have February of 29 days.’ Is this statement true?**

Ans: Yes, it is true.

**Q7. What is a simple pendulum?**

Ans: A small metallic bob suspended by a light inextensible string from rigid support, such that it is free to oscillate without friction about a point, is called a simple pendulum.

**Q8. Define the terms:**

**a) oscillation**

Ans: The to and fro motion of the pendulum is called oscillation.

**b) amplitude**

Ans: The maximum displacement of the pendulum, i.e., the displacement between the mean position and the extreme position, is called its amplitude.

**c) frequency**

Ans: The number of oscillations made by the pendulum in one second is called its frequency of oscillation.

**d) time period as related to a simple pendulum.**

Ans: The time taken by an oscillating pendulum to make one complete oscillation is called its time period.

**Q9. Draw a neat diagram of a simple pendulum. Show the effective length and one oscillation of the pendulum.**

**Q10. How are the time period T and frequency f of a simple pendulum related to each other?**

Ans: Frequency is inversely proportional to the time period ie f=1/T