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15 Jun 2007 20:08:15 IST
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Which of the following are correct..........???
a] Spokes are used in the wheel of a bicycle to increase its Moment of Inertia.
b]The linear momentum and linear velocity vectors are always parallel to each other.
But the angular momentum and angular velocity are not necessarily parallel to each other.
Really, Is moment of Inertia scalar or vector......???Has it got a direction......???
c]The friction acts in different directions....on the two tyres of a bicycle.......
could you explain..........???.......
And please..................please..................please........................
explain it............... and pls dont just give True or false..........
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My name is Jaysun Antony.........
Whatever we do............the final decision is God's.......
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19 Jun 2007 03:05:23 IST
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heeyyyyyy........................No one to help ?????????.........................
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My name is Jaysun Antony.........
Whatever we do............the final decision is God's.......
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19 Jun 2007 03:47:50 IST
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i m trying for 2nd option. all the quantities are in vectors. v = w cross r let w is in i & r is in j dir. :. v will be in k dir. now, L = r cross p (p--> linear mom. i.e in dir. of lin. vel. v) & j cross k is i. so, they both are always parallel acc to me.
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Himanshu Jain
P.E.C.
http://jainhim.blogspot.com/ |
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19 Jun 2007 07:52:38 IST
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but they arent parallel..........says my Master..................
Since L= I.w ..............
dirctn of L will depend both on dirctn of ' I ' and ' w '
So.......my doubt is that........whether I = M r2
But how can I be vector..........?? How can it have direction.........???
Any one pls.........
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My name is Jaysun Antony.........
Whatever we do............the final decision is God's.......
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19 Jun 2007 12:21:16 IST
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opt a and c r correct. when one paddles he imparts an angular velocity on the rear wheel . the wheel in contact with ground experiences a frictional force in forward direction. this is the reason the bicycle moves fwd. the front wheel experiences a backward frictional force due to forward motion of the cycle. the front wheel rotates due to this backward frictional force on it. hence fricton acts in opp dir on both the wheel.
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19 Jun 2007 13:48:06 IST
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Option (c) is correct ...
Bcoz, The rear wheel's experiences frictional force in the forward direction while the front wheel experiences frictional froce in the backward direction .
Explanation:-
When we paddle the cycle we apply force on the paddle which enables the rear wheel 2 move ....
The wheel rotates in the backward direction & cycle moves in the forward direction....
So, the direciton of friction will be in the direction opposite 2 the direction of motion of the rear wheel ....
So, the direction of friction of the rear wheel will be in the forward direction.
On the other hand the front wheel is pushed forward...
So, the direction of friction will be in the backward direction ...
So,the statement " The friction acts in different directions....on the two tyres of a bicycle......." is correct ...
Hope u have understood it .....
Pleazzzz rate me ....... :)
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19 Jun 2007 14:12:13 IST
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A tyre is made up of the outer rim and the spokes.The rim can be considered to be a ring of radius R. So it I would be mR^2. This moment of intertia is about the axis perpendicular to the plane and passing through the center of the ring.The spokes can be considered as rods and their moment of inertia about the center and perpendicular to the plane is lets say I2. So if there are n number of spokes the total moment of interia of the tyre would be =>n(I2)+mr^2 Obviously if n increases moment of inertia of tyre alsoincreases
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19 Jun 2007 14:17:49 IST
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linear momentum P=mv, m is constant .: the ddirection of P and v is same.Angular momentum L=P*(perpendicular component of the position vector of the particle). The position vector can certainly have a direction which different from the direction of the velocity, also aangular velocity can have different direction (clockwise or anticlockwise).
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19 Jun 2007 14:46:57 IST
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ans is A and C
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tic tac toe |
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19 Jun 2007 20:10:49 IST
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And the final question............
Is Moment of Inertia scalar or vector quantity.....???
Or whether it is Tensor.............????..........
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My name is Jaysun Antony.........
Whatever we do............the final decision is God's.......
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19 Jun 2007 20:24:16 IST
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Scalar of course.
For eg in a ring
I = mr^2 , m is scalar, r is scaler so I is scalar.
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20 Jun 2007 15:15:03 IST
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moment of inertia is definetly not a vector quantity eg force=m*accn torque=I*alpha as u can see I has same significance in rotational dynamics as mass. I of a sphere= 2/5mr^2 here u can see that I does not have any direction.
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The woods are lovely, dark and deep.
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And miles to go before I sleep,
And miles to go before I sleep. |
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20 Jun 2007 19:56:23 IST
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M.I' s a scalar quantity...
It depends on d axis but has no direction
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HOPE U GOT IT... |
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20 Jun 2007 20:35:01 IST
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hey rakesh_89.
If I is a vector how can it have "NO DIRECTION"?
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21 Jun 2007 14:19:00 IST
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Moment of Inetia is a tensor
Source { Wiki
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devesh
La parada de tettas |
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21 Jun 2007 14:48:48 IST
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all the options are correct. the reasons for a and c have already been given. ill try to reason out option b.
linear momentum of any body is the product of mass and its resultant linear velocity. so it alway coincides with the direction of the velocity vector.
consider a case where in u have a saucer kept on a smooth floor which is attached to a hook on the floor with a thin massless inextensible string. now u give it an impulse such that it starts rotating abt the hook in the clockwise direction. the direction on the angular momentum of the disc will be in the downward direction if we view the setup from the top (according to the right hand screw rule, or any other rule that may be applied). now we give the saucer an additional impulse which causes it to rotate about an axis passing thru its center in the anticlock wise direction. now wen u calculate the angular momentum abt the hook. it will be the resultant of these two. which can have either of the directions depending upon the magnitude of the two different angular momenta.
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15 Aug 2007 00:50:16 IST
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nah mi is a tensor. NOT A VECTOR or SCALAR
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15 Aug 2007 16:47:52 IST
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ALL 3 R CORRECT.
hmm...angular momentum....none of ur concepts seem clear...
angular momentum is defined about an axis..the axis may or ma not b on the body......angular momentum is given by the vector addition of
Iw and r cross mv
where I is the MI abt centre of mass, w is the angular velocity , v is the linear velocity and r is the perpendicular distance of centre of mass frm the axis
so direction of angular momentum is dependent on both linear and angular velocities and also "r". so it is not necessarily parallel to the angular velocity.
n moment of inertia is NOT a vector.
1st and 3rd hv alrd been answered?
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NO SIGNATURE |
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9 Oct 2007 19:02:54 IST
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joy rakesh said moment of inertia is definitely Not a vector.
anyway
Moment of inertia is a tensor like Pressure.
it does not have a direction in its notation but is physically associated with a sense of direction.
for eg. 2 disks rotating in opp. senses will be said to possess same moment of inertia when at rest but due to their opp. motion they are opp. in physical sense.
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- Gaurav Ragtah (spideyunlimited)
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