Superman attempts to drink water through a very long straw..?

Question

Superman attempts to drink water through a very long straw. With his great strength he achieves maximum possible suction. The walls of the tubular straw don't collapse.
(a) Find the maximum height through which he can lift the water.

(b) Still thirsty, the Man of Steel repeats his attempt on the Moon, which has no atmosphere. Find the difference between the water levels inside and outside the straw.

Answer 1

> (a) Find the maximum height through which he can lift the water.

A column of height "h" can be lifted if the upward forces on it are at least as great as the downward forces.

The downward forces are:
1. The force due to air pressure pushing down on the top of the column. But since Superman achieves "maximum possible suction," that means he's removed all the air from above the column, which means the downward air pressure is zero. So we can ignore this downward force.
2. The weight of the column of water. This equals:
(mass of column)(g)
= (volume of column)(density of water)(g)
= (h × A)(density of water)(g)

where "A" is the cross-sectional area of the straw. (We don't know the value of "A"; but don't worry about that. Trust me, it will cancel out of the final equation).

There is only one UPWARD force on the column of water, and that is due to the water pressure pushing up on the bottom of the column. Presumably the bottom of the column is at the same level where the water in the surrounding tank contacts the air; this means the water pressure there is 1 atmosphere. This means the upward force is:

(water pressure)(cross-sectional area of column)
= (1 atmosphere)(A)

So, to lift a column of height "h":

upward forces >= downward forces

(1 atmosphere)(A) >= (h)(A)(density of water)(g)

Divide boths sides by "A" (see how it cancels out?)

(1 atmosphere) >= (h)(density of water)(g)

Solve for h:

h <= (1 atmosphere) / ((density of water)(g))

> (b) ...on the Moon...Find the difference between the water levels inside and outside the straw.

First, note that "the difference between the water levels inside and outside the straw" is just another way of saying "the maximum height of the water column", which is exactly the same quantity we were finding in part (a). I think they just used different words to throw you off.

Well, the exact same formulas apply; except in this case the upward pressure is "0 atmosphere" instead of "1 atmosphere," and the value of "g" is 1/6 of what it was on earth. Plug those new values into the equation, and solve for h. (Superman no longer seems so strong!)

(In point of fact, liquid water can't exist where there's no atmosphere, because it would boil away. But that's another story.)

Answer 2

Superman Drinking

Answer 3

dogs can't drink with straw because of the fact it does not have lips... dogs's mouth is open at facets... it can't suck something... different than mom's milk in the 1st few months of it is lifestyles... that's why it beverages beverages by it is tongue...

Answer 4

However, if it's Pre-Crisis (or neo-Pre-Crisis stuff like we're getting now), the answers are A) Infinitely high, and B) as much as it takes. Pre-Crisis Superman didn't DO logic or physics. :)

Answer 5

(a) 36 feet.
(b) There will be no difference.