IIT JEE , AIEEE Forum - Physics , Mechanics

jaysunantony

Let me ask u this........ Its tough for me.........See if U could answer........

We are keeping a 1m long stick with flat circlr base [of small area like 2cm²
] in free air/ space.
And we are leaving the support.............and we would see the stick falling/ toppling .

Scientifically speaking, why the stick falls ????..........

What force make it fall................................Any idea.......???....

shreyasnivas

ok its simple.

in a totally ideal situation (NEVER HAPPENS) the stick if kept perfectly vertical, will not fall.(no wind also)

but in our every day life, there is wind factor(the tiniest wind can topple stuff).
and also we dont have a perfect horizontal surface, so a perfectly vertical rod is impossible.

the rod, when pushed by the slightest disturbance, will develop a torque with the
1)normal reaction
2) weight (MG)
(see diag 1)

actually the normal reaction does not affect torque since it passes through the point of rotation.(i put it for the balancing force)

now this weight torque will make it fall faster and faster.

basically a balance can be made if all torque is balanced.we see so many people on tv who balance rocks and chairs and all. there the body is tilted so that the weight is directed opp to normal reaction(diag 2), so no torque, and forces cancel also.

this hopefully asnwers your questions

cheers

shreyas

jaysunantony

So...........can I conclude that the stick wont fall if kept in vacuum where there is no wind factor...........and if I make its base and the surface perfectly flat..............???...

shreyasnivas

yes ofcourse.

catch_arnnie

i don't think air matters too much..

if you keep the stick in a closed room then why should it fall ??

the trick is to keep the center of gravity completely vertical.

if it inclines even a bit ( due to any factor), then it will create a torque wich will topple the stick.

most of the time, people are not able to keep the center of gravity completely vertical, so you see toppling most of the time..

shreyasnivas

yes arnie, but if you read my post, i already stated this.
the CG cannot always be kept vertical since nobady has a perfectly horzontal surface.. if they do, and the stick STILL falls, then surely the wind can be the only reason.

if a stick kept on perfectly horizontal plane in a vacuum and the stick is perfectly vertical, it has no reason to fall! (apart from fluctuations in the earth's rotation ;p)

shreyas

catch_arnnie

i'm sorry but i didn't read your post completely...

i still say, vaccum or air does not matter until wind is not blowing...

shreyasnivas

hey no prob!!
ya your right.. i we dont need vacuum..(i dint specify sorry)
i was only agreeing to what jaysun was saying.

jaysunantony

thanks shreyasnivas and catch_arnnie.......

U made this discussion nice..................

shreyasnivas

youre welcome

akumar_ak

u know why???????
because i blew it over

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