I was asked a simple question and felt that the answer is not, like the question, simple. What happens when you light a match in a space shuttle ?
The other question I have is if a ballet dancer of weight 50kg stands on pointe (on her toes) on one leg and the toe box is roughly 4cm by 2.5cm which is the surface area of contact with the floor, how much force acts on those 5 toes? Does the pull of the leg muscles and tendons help decrease this force?
I tried searching on “flames in microgravity” and got some hits.
It makes a glowing ball of hot gas, with the “fire” burning slowly at the surface.
On the toes question, I’ll make a WAG that from the dancer’s point of view, much of the weight is transferred as pressure against the inside of the ballet shoe, and the shoe transfers it to the 10 square cm described.
And welcome to the Board, typeA!
thanks for the warm welcome and answers, i’ve just discovered the site and its… amazing (provides tons of entertainment for the bored & restless! = )
Welcome to the SDMB, typeA. In addition to the Boards, the Straight Dope Empire™ includes the regular columns of the Perfect Master, Cecil Adams. A hunt through the index for his columns, and the related Staff Reports, is always worthwhile, since the Master sooner or later touches on all questions that keep the Teeming Millions awake at night, such as:
If you lit a match in zero gravity, would it smother in its own smoke?
Figuring out the force on the dancer’s toes is easy–it is equal to the dancer’s weight, which is calculated by:
w = mg = (50 kg)(9.8 m/s[sup]2[/sup]) = 490 N
In your subject line, though, you asked about the pressure on the toes, which is calculated by:
P = F/A = (490 N)/(0.001 m[sup]2[/sup]) = 490,000 Pa
You also asked if “the pull of the leg muscles and tendons help decrease this force” on the toes, due to the dancer’s weight? The answer is no, as the dancer’s weight is the key variable.
No, not really. To expand a little on what has already been said:
The shoes are quite rigid in the toe section, and tight fitting. When the dancer is standing on her toes, much of the weight is distributed to the rest of the foot. Her toes do not bear the full weight. It’s still enough to be damaging over time, but not toe-crushing, as it would appear.
As to a part being played by the muscles and tendons, it wouldn’t surprise me at all. To be en pointe is a very specialized position, and likely a lot of training is required, much of it involving the foot’s physical strength and technique, to support the dancer’s weight and movement.
I have a hunch that the muscles and tendons play a role. For example, my high school physics books include the pull or tension in the muscles when solving an equilibrium problem regarding the body. Perhaps I have to read up some biology…
I have a hunch that the muscles and tendons play a role. For example, my high school physics books include the pull or tension in the muscles when solving an equilibrium problem regarding the body. Perhaps I have to read up some biology…
Wrong. All of the dancer’s weight must be supported by the part of her body that contacts the floor. The OP stated that this consisted of the toes of one foot. Also, based on this picture, the shank of ballet shoes do not appear to extend to the tip of the toes.
None of this has anything to do with the specific question posed in the OP. While there are certainly forces involved with the tendons and muscles in the foot and leg, the force and pressure on the toes, based on the info stated in the OP, is a given.
robby: The pressure on the toe portion of outside of the shoe (the part in contact with the ground) is given by the formula above, but the pressure on the actual flesh of the toes at the end of his/her feet will depend on the degree of support offered by the shoe.
Since the question is ambiguous as to what it means by toes, either answer is correct.
the toe part of toe shoes are wood. you hear the sound of wood on wood if you are close to the stage at a ballet. when dancers are off pointe it comes close to sounding like clogs. in your toe shoes you really are balanced on the knuckles of your toes not on the tippy tip of your toes.
in titanic, kate winslet demonstrates how one balances on toes in ballet. you go up on what most people call tip-toe and then kinda turn it inside out, going up and over to your knuckles. put your hand palm down on the table and then go to the tips with your palm still pointing down, now roll your fingers over to rest with your first knuckle on the table your palm should now face you and your hand should be a straight line from elbow to knuckle.
you really need to hold onto something or someone, when you aren’t in motion on pointe, the reason why the guy is always around a ballerina ready to lend a hand or two. it is very difficult to stay still and balance.
dancer’s feet are horribly messed up from wearing toe shoes. not a pretty sight, but as they get mashed they give the dancer a larger area to balance on.
Ex-ballerina here. It completely depends on the shape of the ballerina’s foot and how much of her actual toe tips come in contact with the tip of the shoe. Since most if not all ballerinas pad the tips of the toes inside the shoes, the toes themselves don’t come in contact with the floor. When I was en pointe, my feet didn’t have many problems at all supporting my weight, as the width of my feet suspended my feet in the shoes, and my weight was pretty well distributed over my whole foot.
The entire box of a pointe shoe (the part of the shoe that covers the toes) is generally made of stiffened layers of canvas and glue, covered with satin. The wooden part on the bottom of the shoe is there to provide support for the arches when the shoe is being flexed en pointe, not the toes. The support for the toe part of the foot is in the box. Dancers don’t wear pointe shoes much past the point (heh) where the box is so broken in that it is no longer supportive. Historically, when dancers first started dancing en pointe, the toes were only regular slipper material, with the toes reinforced with extra sewn seams. Dancers didn’t stay en pointe for very long then, because there was little or no support in the shoe! It wasn’t much different from trying to be en pointe without shoes at all. Much of a dancer’s ability to carry her own weight on her toes depends on the level of support in her shoe, plus the strength of her own feet. And yes, it takes years and years of training to build that strength.
Ballerinas are also taught to walk and stand in certain ways, with excellent posture. Think of the difference of how heavy your feet feel if you walk slumped over and you trudge, versus if you hold your head/neck straight and look straight forward, pulling yourself up into good posture. Dancers are taught to be light on their feet, and make noiseless landings. You learn to roll the foot from toe to heel down onto the floor in order to minimize visible shock and noise. Also, dancers rarely if ever jump or bounce on the very tips of their toes (it’s a specialized step that few dancers are good at or enjoy). The foot normally rolls up to the ball of the heel and then the toe, then rolls back down to a straight foot. Some steps involve putting the weight directly on the tips of the toes, without the intermediate steps, but typically either the dancer isn’t going to be on the point for very long, or will have the other foot en pointe shortly, to distribute the weight among both feet.
and now to dispel some myths…
The toe is not wood. It is layers of canvas and glue. Stiff, but will break in with use, and become useless for support over time. http://www.getpointe.com/capgloss.htm
You are not balanced on the knuckles of your toes. Your feet do arch over (that is correct) but it is the tips of the toes inside the shoes, not the knuckles of the toes. If you stood on the knuckles of your toes inside your toe shoes, you’d probably break your toes.
It’s not super easy, but not super difficult to remain motionless e pointe. Men are more holdovers from tradition and to enable the ballerina to maintain positions that gravity wouldn’t allow her to maintain, and to jump higher, than she would be able to on her own. It has nothing to do with helping her balance en pointe. Generally, when staying en pointe for any length of time, a step is performed where the weight is quickly switched back and forth from one toe to the other. This can be done soundlessly.
But yes, dancer’s feet do get pretty messed up. Mine still are oogly, and I stopped dancing 6 years ago.