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wu :: forums    riddles    easy (Moderators: SMQ, towr, ThudnBlunder, Icarus, Eigenray, william wu, Grimbal)    Water level « Previous topic | Next topic » Pages: 1  Reply Notify of replies Send Topic Print    Author  Topic: Water level  (Read 897 times) Radiohead_man Junior Member     Gender: Posts: 74 Water level   « on: Dec 7th, 2004, 7:48am » Quote Modify A man is in a rowing boat floating on a lake, in the boat he has a brick. He throws the brick over the side of the boat so as it lands in the water. The brick sinks quickly. The question is, as a result of this does the water level in the lake go up or down?   IP Logged I'm a reasonable man get off my case, get off my case. alien Guest Re: Water level   « Reply #1 on: Dec 7th, 2004, 11:36am » Quote Modify Remove ::The water level remains at the same mark.:: « Last Edit: Dec 7th, 2004, 11:50am by alien » IP Logged WombatDeath Junior Member     Posts: 89 Re: Water level   « Reply #2 on: Dec 7th, 2004, 1:47pm » Quote Modify I think the water level would drop.  If you had a small but ridiculously heavy brick weighing a ton it would push the boat down (and therefore the water up) by a lot1.  But when you throw it over the side it would only be moving an amount of water equal to its volume.   1 I suspect that the volume of water moved would be however much water weighs a ton. I wouldn't bet my life (or my boat) on that, though.   Am I right in thinking that the water level would stay the same if your brick was less dense than water? :: IP Logged towr wu::riddles Moderator Uberpuzzler Some people are average, some are just mean.     Gender: Posts: 13730 Re: Water level   « Reply #3 on: Dec 7th, 2004, 1:48pm » Quote Modify It's the same as with the anchor. ::The level goes down, because in the boat the brick displaces it's weight in water, and in the water it only displaces it's volume in water.:: « Last Edit: Dec 7th, 2004, 1:54pm by towr » IP Logged Wikipedia, Google, Mathworld, Integer sequence DB SWF Uberpuzzler     Posts: 879 Re: Water level   « Reply #4 on: Dec 7th, 2004, 6:08pm » Quote Modify There are already threads for this: EASY: Anchor and The Lead Ball IP Logged cyballs Newbie     Gender: Posts: 4 Re: Water level   « Reply #5 on: Mar 9th, 2005, 9:08am » Quote Modify hi..   look at this situation...     when u lift the anchor out of the boat, and put it in water, it is equivalent to putting a lighter weight anchor in the boat. (weight in water is lower)   so obviously, u r pushing it lesser, so the water level is lower IP Logged Karthik Guest Re: Water level   « Reply #6 on: Mar 21st, 2005, 3:54pm » Quote Modify Remove The water level will drop with respect to the boat but will remain same with respect to an observer on land. When you throw the brick (assuming brick is heavy enough) and the brick is in the air, the total weight of the boat reduces and hence the weight of water displaced reduces and hence the volume of boat required to be inside water in order to float, reduces. Hence the boat rises / water dips. WHen the brick lands in water, the water level increases to its previous level but the boat also rises. IP Logged Sjoerd Job Postmus Full Member     Posts: 228 Re: Water level   « Reply #7 on: Mar 22nd, 2005, 4:17am » Quote Modify Let me explain this with an example.   Say, for instance, you have a brick that weighs 10000 pounds, and is extremely small. In the boat, it makes the boat displace about 10000 pounts of water extra. (assume the boat is well enough constructed for this)   Now, you 'trow' it out... The brick does not displace 10000 pounds worth of water, but only the volume it has. The boat however, now displaces 10000 pounds less. The water level would lower, in respect to the viewer on the side, and lower, in respect to the boat... This is an extreme situation, but this helps to show the logic.   The main point is: If the brick sinks, it displaces less water than it would as when it would be in the boat. IP Logged towr wu::riddles Moderator Uberpuzzler Some people are average, some are just mean.     Gender: Posts: 13730 Re: Water level   « Reply #8 on: Mar 22nd, 2005, 6:42am » Quote Modify Anyone who's still unconvinced; take a bucket, a brick and a marker, and go to the bathtub to try it out. IP Logged Wikipedia, Google, Mathworld, Integer sequence DB KArthik Guest Re: Water level   « Reply #9 on: Mar 22nd, 2005, 11:29am » Quote Modify Remove Ya Sjoerd Job Postmus you are right. I guess if the brick would float then it would displace 1000 pnds (which obviously is ridiculous to assume).   IP Logged Pages: 1  Reply Notify of replies Send Topic Print Forum Jump: ----------------------------- riddles -----------------------------=> easy   - medium   - hard   - what am i   - what happened   - microsoft   - cs   - putnam exam (pure math)   - suggestions, help, and FAQ   - general problem-solving / chatting / whatever ----------------------------- general -----------------------------  - guestbook   - truth   - complex analysis   - wanted   - psychology   - chinese « Previous topic | Next topic »

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