PHYSICS

 CLASS 9 Physics   Q1 Name any two basic quantities and write their SI units.  Q2.Name any two derived quantities and write their SI units. Q3 What are the three requirements for selecting a unit of a physical quantity.?  Q4. Define “light year".  Q5. Compare the time periods of two pendulum of length 4m and 25 m.   Q6. State two factors affecting the time period of a pendulum. State the effects also.    Q7. Distinguish between speed and velocity.  Q8. A car is moving with a velocity of 20 m/s. The brakes are applied to retard it at a rate of 2m/s². What will be the speed after 5 s of applying the brakes?   Q9. What does the slope of following graphs represent?  i) displacement-time  graph  ii) velocity-time graph    Q10. Derive the relation: S=ut + ½at² ( any method).  Q11. A body moves from rest with a uniform acceleration and travels 270 m in 3 s. Find the velocity of the  bo...

There are two types of charges because we can establish charges only by loss or gain of electrons present in the orbits of an atom.  By losing electrons  a body gets positively charged and by gaining electrons it gets negatively charged.  Electron is the fundamental charge. It's taken as negatively charged.