A hollow sphere of mass and radius metre is placed with it's centre at origin in -space. It is filled completely with water of mass . So, now the total mass of system is .
A small hole is made at at the bottom and water starts flowing out of the sphere with a constant volume flow rate.
If the maximum distance of centre of mass of the system from origin during the time to the time water completely flows out from the sphere is meters, then what is the value of
Details and assumptions
are distinct integers such that .
While calculating centre of mass of the system don't consider the water that flown out from the sphere. Only consider the water that is present inside the sphere.
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
Invert the universe so that the water is now flowing out through top. Now, at a certain instant, the surface of water(blue) is at distance x from the center.
At this instant, mass of water body is given by:
m w = ∫ x 1 ρ π ( 1 − t 2 ) d t
where ρ is the density of liquid.
therefore, center of mass of water body is given by
x 1 = m w ∫ x 1 ρ π t ( 1 − t 2 ) d t
this means that center of mass of whole system is:
K = ∫ x 1 ρ π ( 1 − t 2 ) d t + m ∫ x 1 ρ π t ( 1 − t 2 ) d t
where m is mass of container.
now, put f ( t ) = ρ π ( 1 − t 2 ) , then the equation reduces to:
K = ∫ x 1 f ( t ) d t + m ∫ x 1 t f ( t ) d t
now putting the condition d x d K = 0 , we get that:
x = ∫ x 1 f ( t ) d t + m ∫ x 1 t f ( t ) d t
⇒ x = K (when K is maximum)
Now, integrating and cross multiplying, we get:
x 4 − 6 x 2 + 2 4 x − 3 = 0
solving this equation yields the required value of x , which is 1 2 4 1 − 9 4 1 m e t r e
thus, answer is: 1 2 + 9 + 4 = 2 5