__JSUNIL TUTORIAL,SAMASTIPUR__

__Class 9__^{th}(SA-II)

^{Physics Assignment-I (For month of November)}

^{Chapter:Gravitation}Q1. A block weighing 1.0 kg is in the shape of a cube of length 10 cm. It is kept on a horizontal table. Find the pressure on the portion of the table where the block is kept. (ans. 1000Pa)

Q2. Find the thrust acting on the human body due to atmospheric pressure. Take the surface area of a man of middle size to be 1.5m

^{2 }and atmospheric pressure (1atm) =1.013×10^{5 }Pa.^{ }(ans.15.2 ton wt)Q3. Calculate the mass of a body whose volume is 2 m

^{3}and density 0.52 g/cm

^{3}. (ans. 1040 kg)

Q4. A dining hall has dimensions 50m × 15m × 3.5m. Calculate the mass of air in the hall. Given, density of air =1.30kg/m

^{3}. (ans. 3412.5 kg)

Q5. A thread of mercury of 10.2 g is in a tube of uniform cross section 0.1cm

^{3}. Calculate the length of thread. The density of mercury is 13.6g/cm

^{3}. (ans. 7.5cm)

Q6. A cubical block of water is dipped completely in water. Each edge of the block is 1cm in length. Find the buoyant force acting on the block. (ans. 10

^{-2}N)

Q7. A body of mass 2.0 kg and density 8000 kg/m

^{3}is completely dipped in a liquid of density 800 kg/m

^{3}. Find the force of buoyancy on it. (ans. 2N)

Q8. A piece of iron of density 7.8 × 10

^{3}kg/m

^{3}and volume 100 cm

^{3}is totally immersed in water. Calculate (a) the weight of the iron piece in air (b) the upthrust and (c) apparent weight in water. (ans. (a) 7.8N (b) 1N (c) 6.8 N)

Q9. A solid body of mass 150g and volume 250cm

^{3}is put in water. Will the body float or sink.

Q10. A solid of density 5000kg/m

^{3}weights 0.5 kg in air. It is completely immersed in water of density 1000kg/m

^{3}.

(a) Calculate the apparent weight of solid in water.(ans. 0.4 kg)

(b) What will be its apparent weight if water is replaced by a liquid of density 8000kg/m

^{3}? (ans. 0)Q11. The mass of a block made of certain material is 13.5 kg and its volume is 15 × 10

^{-3}m

^{3}. Will the block float or sink in water. Give reason for your answer.

Q12. (a) What is the density of air in NTP? (b)What is the unit of relative density?

Q13. (a) When does a body sinks in a fluid?

(b)Why does a balloon filled with hydrogen gas rise up against gravity?

Q14. (a) Which has greater density: 1 kg of iron or 2 kg of iron?

(b)If a hollow sphere and a solid sphere are both made of the same amount of iron, which sphere has greater average density?

Q15. (a). A body weighs 10 N in air and 8 N when fully immersed in water. How much is the buoyant force acting on the body?

(a) Why are the buoys making the channel in a river are hollow spheres?

Q16. State one important effect produced by the buoyant force exerted by water.

Q17. Where does a solid weigh more- in air or in a liquid?

Q18. Name two factors on which the buoyant force depends?

Q19. What is the relationship between the buoyant force on an object and the liquid displaced by it?

Q20. The relative density of mercury is 13.6. What does this statement mean?

Q21. The density of turpentine oil is 840 kg/m

^{3}. What will be its relative density?

Q22. Explain why big boulders can be moved easily by floods.

Q23. Why is a slight blow on a cork of bottle fully filled with a liquid sufficient to break the bottle?

Q24. Why is it easier to walk on soft sand with a flat shoe than a pencil-heeled shoe?

Q25. Lead has greater density than iron and both are denser than water. Is the buoyant force on a lead pencil greater than, less than or equal to the buoyant force on an iron object of same volume?

Q26. Why do you feel lighter when you swim?

Q27. Why is a bucket of water lighter when in water than when it is taken out of water?

Q28. Why it is easier to swim in sea water tan in river water?

Q29. Two different objects are completely immersed in water and undergo same loss in weight. Is it necessary that the weight of these objects in air be also the same?

Q30. If two equal weights of unequal volumes are balanced in air, what will happen when these are completely dipped in water?