Register to reply 
Kinematic questions(velocity of 2 contact points) 
Share this thread: 
#1
Feb2813, 11:58 PM

P: 163

in the picture below
http://tinypic.com/view.php?pic=9riq9l&s=6 if we know the angular velocity of the gear on the left, as well as their current distance from contact point, what can we say about the velocity of the right rod at the contact point at anytime t? we know it is not just the velocity of the contact point of the left rod because the right rod can be sliding along the left rod. but how do we find its exact velocity? 


#2
Mar113, 05:42 AM

Sci Advisor
HW Helper
P: 6,684

AM 


#3
Mar113, 01:50 PM

P: 163

how exactly do we relate the velocity of the contact point of left rod and right rod? we know the velocity of left rod at contact point, but certainly right rod's velocity at the contact point wouldn't be the same since it is sliding along the left rod right? 


#4
Mar213, 09:48 PM

Sci Advisor
HW Helper
P: 6,684

Kinematic questions(velocity of 2 contact points)
Consider the situation shown with the tip of the right rod is contacting the body of the left rod. You have to relate the velocity of the tip of the right rod to the velocity of the point that it is in contact with: ω_{r}L_{r} = ω_{l}r_{l} + v where v is the speed of the end of the right rod along the length of the left rod (ie. dr_{l}/dt)/ I haven't worked it out but I think that is how you have to do it. The trick is to express v in terms of the angular velocities of the two rods. AM 


#5
Mar313, 12:38 AM

P: 163

my first guess is also the equation you have above, but what i have trouble is that, should vector v in your equation be based on the geometry of the two rods at current time t? or t = t +dt? to be it makes more sense to use the time at t+dt or else the left rod will end up in a awkward position. 


#6
Mar313, 09:14 AM

Sci Advisor
HW Helper
P: 6,684

AM 


#7
Mar313, 11:32 AM

P: 163

right but the angle between two rods at the current time? or some dt later?? if I break the velocity into two component, the component that is along the contact point of left rod , and the velocity tangential to the left rod. After some dt later, the position of the contact point of my right rod would be a the position of the contact point of the left rod, minus some distance away from the center of the left rod. I don't know if my question make sense, sorry about the confusion. 


#8
Mar313, 01:23 PM

Sci Advisor
HW Helper
P: 6,684

AM 


Register to reply 
Related Discussions  
Applying force to a flat object with contact points  Introductory Physics Homework  4  
2D kinematic questions  Introductory Physics Homework  5  
Near and far points with contact lenses  Introductory Physics Homework  2  
Weight distribution, multiple points of contact  Classical Physics  1  
Distance between polygons in 3d? (points of contact as a function of time)  General Math  4 