Science practice questions class9

Practice Questions, Science

Q1. Write the value of G in S.I. unit.

Q2.What will be the value of g at centre of the Earth?

Q3.State Newton's universal law of gravitation.

Q4.Write the differences between g and G.

Q5.Write the differences between mass and weight.

Q6.Write the differences between distance and displacement.

Q7.Write the differences between speed and velocity.

Q8.Define acceleration.

Q9.State Newton's first law of motion.

Q10.State Newton's second law of motion .

GRAVITATION

Q11. What are fluids?
Ans :Fluids are the substances that flow and lack a fixed shape, exert pressure in all directions and this pressure depends on the height of the fluid column above.

Q12. What is buoyant force ?
Ans: The upward force employed by a fluid which makes objects appear lighter when submerged, is called the buoyant force.
According to Archimedes' principle, the buoyant force equals the weight of the displaced fluid.

Q13. State Archimedes' principle.
Ans: Archimedes' principle states that whenever an object is immersed in a liquid (fully or partially), the liquid exerts on upward force upon the object.The amount of that force is equivalent to the weight of the liquid displaced by the object.

Q14. Write the applications of Archimedes principle.
Ans: (a) In evaluating relative density
(b) In designing ships and submarines.
(c) In making lactometers and hydrometers.

Q15. What is density?
Ans: Mass per unit volume of an object is called its density.
Density = Mass/volume

Q16. What is the S.I. unit of density?
Ans: kg/m₃

Q17. What is relative density ?
Ans: The ratio of density of a substance to the density of water is called relative density of the object.
Relative density = (density of substance)/(density of water)
Q18. What is the S.I. unit of relative density?
Ans : Relative density has no unit. It is a pure number.

Q19. Why is water chosen as a reference?
Ans: Water is present everywhere on the Earth so it becomes easier to evaluate the density of a substance in relation to water.

Q20. When an object sinks or floats in water?
Ans: If relative density of an object is greater than 1, it sinks in water.
If relative density of an object is less than 1 , it floats on water.