Motion along an inclined plane that can be rotated along x and z axes,
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Posted 01 August 2001 - 06:25 PM
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Posted 02 August 2001 - 12:57 AM
> exceeded the static frictional force. i.e
> Fnet > Mu_static * FNormal
I think your calculation in the code is wrong: I think you need:
fFnet = Fparallel - ( coefKineFriction * Fperpendi );
i.e. this gives the force due to gravity but opposed by friciton.
If you do it this way the answer just drops out: If fFnet is negative the object just doesn''t start moving.
If the object can move freely you need something more complex: the net force is vector, with acceleration due to gravity down the slope and friction opposing the direction of motion.
> Do i have to calculate Parallel and Perpendicular forces for
> each Azes seperately ?
No: you can do all calculations in a coordinate free way, i.e. using just vectors and vector operations. Your code is already most of the way there, with gravity and the plane normal as vector inputs. There are other things you can do, such as use the inner product instead of sin and cos in the first two lines, and using vector scaling in the last eight lines.
As for whether/when to use static/dynamic friction, this is one of the trickiest questions in physics to answer. In theory there''s a simple dividung line between them, between situations where objects are moving and situations where they are not. But in a simulation it''s difficult to draw the line between such situations.
You approach sounds fine for your current simulation, but as you add in rotation and other more complex behaviour you may find it needs to be much more sophisticated.
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Posted 02 August 2001 - 04:43 PM
>I think you need:
>fFnet = Fparallel - ( coefKineFriction * Fperpendi );
>i.e. this gives the force due to gravity but opposed by >friciton.
Hey thanks for the correction. i could'nt figure out why the object moved in the opposite direction of the tilt i.e when i tilted the surface towards me, the object slided away from me.
That was bcos i was summing up the forces. With the formula correction u suggested the object is sliding in the right directions.
>If the object can move freely you need
>something more complex:
>the net force is vector, with acceleration
>due to gravity down the slope and friction
>opposing the direction of motion.
Okay say i were to convert the net force to a vector. How do i go bout doin that. Do i create a unit vector and scale it with the scalar value ( fFnet ) ?
>There are other things you can do, such as use the
>inner product instead of sin and cos in the
>first two lines
i didnt quiet get u. what is the inner product ?
i'm workin on the transition of Frictional force from static to kinetic.
i'll let u know once i get that working.
Thanks for the post
Edited by - vinny_ys on August 2, 2001 11:46:14 PM