Light — PHYSICS STD 9 — Question

Why is an aneroid barometer called so?

A test tube weighing 17 gf , floats in alcohol to the level P . When the test tube is made to float in water to the level P, 3 gf of the lead shots are added in it. find the R.D. of alcohol.

Will a body weigh more in the air or in the water when weighed with a spring balance? Why?

The sound of an explosion on the surface of lake is heard by a boatman 100 m away and a diver 100 m below the point of explosion.
1.Of the two persons mentioned (boatman and diver), who would hear the sound first?
2.Give reason for your answer in (i).
3.If the sound takes ‘t’ seconds to reach the boatman, approximately how mcuh time it will take to reach the diver?

A wooden block floats in water with two third of its volume submerged.
(1) Calculate density of wood.
(2) When the same block is placed in oil, three quarter of its volume is immersed in oil.
Calculate the density of oil.

How many images will be formed when an object is placed between two parallel plane mirrors with their reflecting surfaces facing each other? Why do more distant images appear fainter?

How will you show that there is vacuum above the surface of mercury in a barometer? What name is given to this vacuum?

Define the time period of a simple pendulum,

(a) What do you understand by the term order of magnitude of a quantity?
(b) Why are physical quantities expressed in the order of magnitude? Support your answer by an example.