Brain Teasers
Clever Jenny XII
Situation
Situation puzzles (sometimes called lateral thinking puzzles) are ones where you need to ask lots of yes or no questions to figure out what happened in the situation. These are good puzzles for groups where one person knows the puzzle and answers the questions.Situation
Jenny pulled up to her Mom's house and cut the engine. "Oh, Mom! I hope you have something quick for dinner; I'm starved!"
"I'm just going to do some spaghetti with a red sauce; is that OK?"
"Now, Mom! You know I love your pasta however you make it!"
Her Mom unlocked the door and Jenny took in the bags from their shopping trip.
"I can get the water going on the stove. You want me to put the cold stuff in the fridge?"
"Thanks, Honey! I'm going to start on the sauce. You know, I always use the stuff in a glass jar and then mess with it a bit, don't you?"
"Yup, but it's how you do the messing that I need to learn!"
Jenny stood with her hands in her pockets as she watched her Mom struggle with the jar of sauce, tapping the metal lid with the edge of a knife.
"Oh, darn! This jar just doesn't want to open! Jen, can you give it a try for me, please?"
Mom handed the jar to Jenny, who reached out her left hand and took it by the top. She said, "OK, here is where I do my magic trick!"
She then took the jar top by her other hand and held it up, grinning, saying, "Now watch this, Mom! Nothing up my sleeve!"
The jar opened instantly, with hardly any effort!
What trick had Jenny performed?
"I'm just going to do some spaghetti with a red sauce; is that OK?"
"Now, Mom! You know I love your pasta however you make it!"
Her Mom unlocked the door and Jenny took in the bags from their shopping trip.
"I can get the water going on the stove. You want me to put the cold stuff in the fridge?"
"Thanks, Honey! I'm going to start on the sauce. You know, I always use the stuff in a glass jar and then mess with it a bit, don't you?"
"Yup, but it's how you do the messing that I need to learn!"
Jenny stood with her hands in her pockets as she watched her Mom struggle with the jar of sauce, tapping the metal lid with the edge of a knife.
"Oh, darn! This jar just doesn't want to open! Jen, can you give it a try for me, please?"
Mom handed the jar to Jenny, who reached out her left hand and took it by the top. She said, "OK, here is where I do my magic trick!"
She then took the jar top by her other hand and held it up, grinning, saying, "Now watch this, Mom! Nothing up my sleeve!"
The jar opened instantly, with hardly any effort!
What trick had Jenny performed?
Hint
Remember, the lid is metal and the jar is glass.Answer
When she took her left hand out of her pocket, Jenny held the metal lid, warming it up and causing it to expand slightly. When she moved the lid to her right hand, it warmed and expanded a bit more. At that point, the jar lid turned easily and could be removed.Hide Hint Show Hint Hide Answer Show Answer
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Comments
It was nice!
I had trouble understanding what she held by what. Also, does this trick really work? It doesn't seem likely that the human body can sufficiently produce enough heat to expand a jar lid. Plus, if one hand can't heat it enough, how does switching it to the other hand help? They should both be the same temperature!
Good question! While the left hand is warming up the lid, the lid is cooling off the fingers. Going to the right hand, which is still warm, will add a bit more warmth. Not a whole lot of heat is needed to expand the thin metal lids on some pasta sauce jars.
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Maybe that explains why, when you can't get the lid off yourself, the person you hand it to gets it off first try!
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How long did she wait for her mom to try...
wouldn't her hands be colder than her mom's from putting the things in the fridge?
wouldn't her hands be colder than her mom's from putting the things in the fridge?
(What perrygf says is true...)
Great teaser, I said that she heated it/ warmed it up, so that's close enough!
I think...
Hehe, great job
Great teaser, I said that she heated it/ warmed it up, so that's close enough!
![](/images/emote/icon_cool.gif)
![](/images/emote/icon_confused.gif)
Hehe, great job
![](/images/emote/icon_cool.gif)
![](/images/emote/icon_biggrin.gif)
Haha, funny comment zero
Not that her hand would cool down that much, for the same amount of energy transferred to the lid, it increases the temperature of the lid more than her hand... nice teaser though
Not that her hand would cool down that much, for the same amount of energy transferred to the lid, it increases the temperature of the lid more than her hand... nice teaser though
![](/images/emote/icon_biggrin.gif)
Why not use the hot water for the pasta?
Eh = cm(delta)T
delta(T) would be far greater than for the human body.
Eh = cm(delta)T
delta(T) would be far greater than for the human body.
That's an option, too, but then Jenny wouldn't be able to do her magic trick!
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oh my goodness i love clever jenny story things so much! keep making more
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Thank you so much for your nice comments! Jenny is a combination of several wonderful ladies I have known - grammas, aunties, my own Mom, and my Mother in Law! That great lady recently passed on at the age of nearly 102. Some of the episodes I have posted are in memory of her!
awe wow that soooooo cool! haha. wow - 102! i hope i live that longgg.
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I know this aa a fact, because I often perform this tasks with mental tops and glass jars. Incidently, Jenny's action is safer...
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oh come on....if the human body could produce enuf heat to expand a metal cap, i wouldnt have to switch on the gas everytime i needed to open a glass jar!!!
I like the Clever Jenny series. In this case, though, why didn't her mother's hand have this effect already? Am I missing something?
Perhaps the solution is that when the first person gives up, they have already loosened the lid a bit one way or another, and inevitably you give it to the next person just at the moment it's got easier, so you look useless! In England they call this Sod's Law, i.e. things always happen so as to mess you up.
Perhaps the solution is that when the first person gives up, they have already loosened the lid a bit one way or another, and inevitably you give it to the next person just at the moment it's got easier, so you look useless! In England they call this Sod's Law, i.e. things always happen so as to mess you up.
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