User:Santosh kurmi/sandbox

These are the helpful question and their answer for modern graded science and environment of class 8.

1.Measurement

1. What is physical quantity?

-A physical quantity is that quantity which can be measured directly or indertly.for eg;density,area,volume,time etc.

2. What is fundamental quanties?

-Those physical quantity which do not depend upon other quantities are called fundamental quantities.For example:length,time,temperature etc.

3. What is derived quantity?

-Those physical quantities which are to be expressed in terms of other fundamental quanties are called derived quanties.for eg: velocity,area,volume etc.

4. What is measurement?

-Measurement is the comparison of an unknown quantity with a known standard quantity.

5. What is unit?

-The standard quantity with which we carry out the measurement of any physical quantity of the same kind is called unit.

6. Write the importance of measurement?

-The importance of measurement are given below;

i) Measurement helps in selling and buying goods.

ii) It is important in performing scientific experiments to establish truth about a physical phenomenon.

iii) It helps to obtain the accurate results about physical quantities.

iv) It helps in performing experiment for making our daily food.

7. What is standard unit?

-The unit which is accepted all over the world is called standard unit.for eg; metre,kilogran,second etc.

8. What is CGS,MKS MKS and SI system?

-The type of system in which length is measured in centimetre,mass in gram and time in second is called CGS system.It is also known as French system of units.

-The type of system in which length is measured in metre,mass in kilogram and time in second is called MKS system.

-The type of system in which length is measured in foot,mass in pound and time in second is called FPS system.It is also known as British system of units.

-The system which are accepted all over the world and recommended by world class scientist and extended and improved version of MKS system is called SI system.

9. What are fundamental and derived units?

-The units which are used to express fundamental quantities are called fundamental units.for eg;metre,kilogram,second etc.

-The units which can be expressed in terms of two or more fundamental units are called derived units.for eg;square metre,cubic metre etc.

10. What is mass?

-The amount of matter contained in a body is called mass.It si unit is kilogram.

11. What is time?

-The duration between any two events is called time.

12. What is weight?

-The force of gravity applied on a body is called weight.weight is measured by a spring balance and its unit is N.

13. Why the unit of area is derived unit?

-The unit of area is derived unit because the unit of area is formed by using two times unit of length of fundamental unit.

14. Write difference between SI and CGS system.

-The difference between SI and CGS system are given below;

for SI system; i) It is accepted all over the world.

ii) It is more advance than CGS system.

iii) It is the extended version of MKS system and recommended by world class scientist.

for CGS system; i) It is not accepted all over the world.

ii) It is less advance than SI system.

iii) It is the system in which length is measured in centimetre,mass in gram and time in second.

15. Write any 4 difference between mass and weight?

-The difference between mass and weight are given belnw;

for mass; i) The amount of matter contained in a body is called mass.

ii) It is same all over the world.

iii) Mass is measured by beam balance.

iv) Mass=weight(W)/acceleration due to gravity(g).

for weight;

i) The force of gravity on a body is called weight.

ii) It is different in all over the world.

iii) It is measured by spring balance.

iv) Weight=mass(m)Xacceleration due to gravity.

16. What are sub-multiples and multiples?

-The unit which are smaller than si unit are called sub-multiples unit.for eg; cm,gram etc.

-The units which are greater than si unit are called multiples. For eg;km,mile,minutes etc.

17. What is solar day?

- The time taken by the earth to rotate once about its axis is called solar day.

18. What is Metric system?

-The system of measurement that uses metre,kilogram and litre as basic units.

18. Write seven fundamental units of si units.

-The seven fundamental units are give below;

i)length(l):metre(m).

ii)mass(m):kilogram(kg).

iii)time(t):second(s).

iv)temperature:kelvin(K).

v)current:ampere(A).

vi)luminous intensity:candela(cd).

vii)amount of substance:mole(mol).

19. What is metrology?

-The science of measurement is called metrology.

2.Force and Velocity

20. What is force?

-Force is an agent that tends or changes to change the state of rest or motion of an object.

21.What is reference point or reference frame?

-A reference point or reference frame is the fixed point/place/obje