Question

A stream line body with relative density d1 falls into air from a height h1 on the surface of a liquid of relative density d2 where d2 >d1 . Then time of immersion of the body into the liquid will be:

Answer 1

Explanation:

To determine velocity of body at surface;

From motion equations:

v

2

=u

2

+2as

⇒v

2

−0=2gh

1

⇒v=

2gh

1

Apparent acceleration due to gravity in liquid

g

′

=

mass

Change in weight

=

Vd

1

Vd

1

g−Vd

2

g

=(

d

1

d

1

−d

2

)g=−(

d

1

d

2

−d

1

)g

Since d

2

>d

1

,g

′

is retarding motion.

Time taken t=

∣g

′

∣

V

=

(

d

1

d

2

−d

1

)g

2gh

1

=

g

2h

1

(

d

2−d2d1)