Solutions of physics online class test - 2 of class 8

 1.A body X floats on water, a body Y sinks in water.The density of the body X is .......... than the density of body Y.

Ans. Less

2.The buoyant force experienced by a body when floating in Indian ocean is .......... that when floating in Dead sea.

Ans.  equal to

3.A body while floating .......... in water than in Glycerine.

Ans.deeper

4.Relative density of A is 2.7 . 150 cubic cm of A would have a mass of......... .

Ans. Relative density  of A = 2.7

V = 150 cm³

Mass of 150 cm³ = ?

Relative density= density of substance/density of water at 4 degree Celsius.

RD × density of water=density of a substance

Density of a substance=RD × density of water

                                         = 2.7 × 1gcm-³

                                         = 2.7 gcm-³

ρ= M/ V

ρ× V=M

M=ρ× V

  = 2.7 gcm-³ × 150 cm³

  = 405.0 g

  = 0.405 kg

5.A body A sinks in Alcohol but floats in Mercury.Density of A is in between ............ and ............ .

Ans.0.8g per cubic cm ,13.60 g per cubic cm

6.......... is the volume of an object of mass 600 kg if its density is 0.8 g per cubic cm.

Ans.V= ?

M= 600 kg

ρ=0.8 gcm-³

   = 0.8 × 1gcm-³

   = 0.8 × 1000 kgm-³

   = 800 kgm-³

ρ= M/ V 

ρ× V = M

V = M / ρ

V = 600 kg / 800 kg m-³

   = 3/4 m³

  = 0.75  m³

= 7.5 × 10 -⁷ cm³

7.The mass of an empty density bottle is 100 g, it is 145 g when filled completely with water and 135 g when filled completely with a liquid.Then density of liquid is ......... .

Ans.M₁=100 g

M₂=145 g

M₃= 135 g

ρ=?

ρ=M₃ - M₁ / M₂ - M₁

   = 35g / 45 cm³

   = 7/ 9 gcm-³

   = 0.77777 gcm-³

   = 777.78 kg m-3

8.Name a substance whose density is 8.9 g per cubic cm as per your physics textbook.

Ans. Copper.

9.Volume of substances varies with change in temperature but .......... remains constant.

Ans.mass

10.The density of air is 1.30 g per cubic dm. Express it in 1) g per litre 2) g per cubic cm 3) kg per cubic m

Ans.ρ= 1.30 gdm-³

            = 1.30 g/ dm³

            = 1.30 g / 1 l ( 1L = 1dm³ )

            = 1.30 g / 1000 cm³ (1L = 1000 cm³)

            = 1.30/1000 gcm-³

            = 0.00130 gcm-³

            = 0.00130 × 1 gcm-³

            = 0.00130 × 1000 kgm-³ (1gcm-³ = 1000 kgm-³)

            = 1.30 kgm-3

So,the correct answer is option A.

1.30 ,0.00130 ,1.30.