can someone explain this?

[sdnstud]

Straight out of EK's website:

A large boat filled with many cannon balls floats in a small pond. If the cannon balls are dropped over the side and into the pond, the water level of the pond:

A. falls slightly and the boat rises out of the water slightly.
B. falls slightly and the boat sinks into the water slightly.
C. rises slightly and the boat rises out of the water slightly.
D. rises slightly and the boat sinks into the water slightly.

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[silkworm]

My guess is C, boat is lighter, so it floats higher, the dropped ball will add volume to the pond, so the water level rises.

 

[IndyZX]

Damn. I have no idea.

Something to do with Archimedes Principle, though...

 

[vinoyp]

I'm going with A. With the cannonballs in the boat, the amount of water that is displaced is equal to the weight of the boat and the cannonballs, since the boat is floating. Archimedes Principle.

When the cannonballs are dropped overboard, these will not float. They will sink. They will displace a less amount of water, which will simply be equivalent to the volume of the cannonball, NOT THE WEIGHT OF THE CANNONBALL.

Therefore, the pond level will fall. And, the boat will rise a little, sure sure.

--Vinoy

 

[blebl34]

all i have to say is beyond the scope of mcat

 

[smaroof]

My guess is C, the dropped ball will add volume to the pond, so the water level rises.

e

 

[IndyZX]

all i have to say is beyond the scope of mcat

Maybe, but you should be careful. Some of those Archimedes Principle problems require you to have your brain wrapped firmly around the concept.

 

[blebl34]

Maybe, but you should be careful. Some of those Archimedes Principle problems require you to have your brain wrapped firmly around the concept.

true true, just never seen anything "that" involved, but who knows, saturday may rip me a new one

 

[shaq786]

What is the answer??????????????????

 

[rcd]

i'm going with a.

my reasoning:

boat - 1kg, 9.8N, 9000L
ball - 1L, 100kg, 9800N (chose a big number because it simplifies things)

ok, so the water is pushing at (9809.8)N up (the boat isn't moving, forces must be equal)

now, you take the ball out. the fluid doesn't need as much force to shove the boat up so the boat rises (MUCH less of its 9000L volume is now submerged then before). the water level lowers because less boat is in it.

now put the super heavy ball into the water. it only displaces 1L. yeah, common sense should be that the water level just lowered and the boat's leve rose.

 

[Pontifex Maximus]

The answer is A. Guaranteed. This is one thing from physics I remember