Inspired by... sushi?

Classical Mechanics Level 2

Jake is on vacation in Japan (for real!), preparing to enjoy Japanese cuisine when he realizes that breaking chopsticks from the end is far easier than from the middle.

What concept explains this?

Time Force Torque Quantum mechanics It's a mystery :o Relativity Energy String theory

6 solutions

Jake Lai
Jun 15, 2015

Chopsticks are joined at the top. This joint is a pivot point; if I need some minimum torque to break apart the chopsticks, then by

$\tau = r \times F$

we have less force required for a longer distance from the pivot.

I feel jipped. You didnt mske it clear that he was breaking apart "connected" chopsticks. You only stated "breaking" them. it should have been more clear.

Scott Musgrave - 5 years, 11 months ago

But it still would have been the same answer. If you're applying force at the pivot point it's going to be more difficult to break them as compared to applying force at the ends of the chopstick. If you held the chopstick at both ends and tried to break it in half, you would still be applying torque.

Brittany Crooks - 5 years, 4 months ago

Happy vacation!

Sravanth C. - 5 years, 12 months ago

This tricked me! I totally dismissed the clue of "breaking" as "applying force" .. however, might be a case for ambiguity in the question, as the example shows force rather than torque.

http://cdn4.explainthatstuff.com/wheelbarrow2.png

Gary fry - 5 years, 11 months ago

Have a nice vacation and いただきます :3

Trung Đặng Đoàn Đức - 5 years, 12 months ago

Please explain why rest of the options are wrong

Agnishom Chattopadhyay - 5 years, 12 months ago

Torque is best used to explain it.

Jake Lai - 5 years, 12 months ago

torque= distance from pivot * force applied

since distance is greatest at the other end, maximum torque is provided there

chopsticks can easily be opened from any point..but we need to apply least force when we break it from one ends

Yoogottam Khandelwal - 5 years, 12 months ago

Another way - take two circles one with smaller radius and other with larger radius , mark 4 cm arc on both the circles , connect both the ends to the center of the circle . Now imagine one line connecting the one of the end point of the circle as an imaginary door(initial position - same for both circles) Now when we will aplly same force to cover the 4cm arc see which has covered greater area. This gives the definition of torque

sandeep Rathod - 5 years, 11 months ago

I did not ask why torque is correct. I am more interested in knowing why the others are wrong.

Because this is an one option correct MCQ, it is the author's responsibility to prove that exactly one option is correct.

Agnishom Chattopadhyay - 5 years, 11 months ago

Thought it was pressure. Anyhow, lucky you! Enjoy your vacations! (;>)(<3)!

Prarthna Roy - 5 years, 11 months ago

I was thinking why would you(Jake) break chopsticks and how it is easier to break from the end (since breaking something from the middle is easier than end), i didn't knew it was all about mode of grasping chopsticks and chopsticks were pivoted.

wihi miuli - 5 years, 11 months ago

Enjoy your vacations! @Jake Lai

Mehul Arora - 5 years, 12 months ago

Sorry I understood it as a plane wodden ruler type thing. Suppose it was the thing which I assumed then too the same explanation would be applicable?

Here the mass would be uniform so the COM would be the center point(seems all the mass is concerntrated at that point) . So I would prefer far end

sandeep Rathod - 5 years, 11 months ago

Breaking the chopsticks versus splitting the chopsticks. You tricked me as well.

Frank Higgins - 5 years, 11 months ago

reacherd feynman once tried to solve this problem..............after few chopstick brecking and little experimenting he did not concluded anything.......as far as i know but this seems pretty logical.......but can't be perfect...

pranav patil - 5 years, 7 months ago

it's beacause of bending moment not torque when trying to break it from the ends that's cuz max bending moment in the middle and that's leads to max stresses on the beam 😒

Omar Mahmoud - 5 years, 11 months ago

Ayushmaan Sharma
Jun 21, 2015

torque=force*distance and the other end of chopstick is acting as pivoted point(fulcrum) so when we will break the chopstick from one end, the distance will be maximum so the torque will be increased and if we will break it from the middle the distance will decrease and a larger force will be required

Derek Lazar
May 2, 2016

Torque is the product of a radius and force. It describes twisting force. A bending moment would be a better answer, imo.

Euan Zhang
Jul 19, 2015

Ask your dad, he probably took physics. Btw, the answer is torque. :^)

Brian Lee
Jun 21, 2015

Chopsticks are joined at one end so if you apply a force farther from the joint (the other end lol) then there's more torque, therefore easier to break.

Sumit Singh Gaur
Jun 20, 2015

Because of the perpendicular length between CM as axis of rotation and point of action of force is maximum at corners,, so torque will required minimum to rotate about center if mass,,

Inspired by... sushi?

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