Solving 2D Velocity at Point P on a Rigid Body - HELP ME!

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SUMMARY

The discussion focuses on calculating the velocity at a point P on a rigid body in 2D using the equation derived from a referenced paper. The equation incorporates the linear velocity of the center of mass (CM) and the angular velocity of the rigid body. The user initially miscalculated the velocity due to confusion over the units of angular velocity, which is expressed in radians per second. The final calculated velocity at point P was determined to be (22.5, 17.5), which the user questioned due to its seemingly high value.

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This discussion is beneficial for physics students, mechanical engineers, and anyone involved in the study of rigid body dynamics, particularly in 2D motion analysis.

porquilho
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Hi. I think this is my 1st post here but I browse a lot on the forum :smile:
I was trying to know the velocity at a point on a rigid Body (in 2D) and i found this equation on a paper:
http://members.fortunecity.de/porquilho/eqVel.jpg
where:
Vap = velocity at point P (body A)
Va1 = Linear Velocity of the Rigid Body CM (m/s)
w1 = Angular Velocity of the Rigid Body (rad/s)
rap with a invers "T" = the perpendicular distance vector from the CM to point p.

Im working on 2 dimension here so angular velocity is just a scalar

The question i have is the unreal result that this equation gives to me, for exemple:
Va1(0, -5)
w1=1.5;
rap(-5,-20) -> now we take the prependicular vector (90º to the left)
rapT(20, -5);
and if I am not mistak making the calculations
Vap = (0,-5) + ( 1.5*20 + 1.5*(-5))
Vap = (0,-5) + ( 30+(-7.5))
Vap = (0,-5) + 22.5 = (22.5, 17.5);
Vap=(22.5, 17.5)

I think this value is too high, are my calculations wrongs ?
HELP ME
 
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Why is that "unreal"? This object is not moving very fast in translation but it is spinning like heck and it's pretty darn big.
 
maybe ur right

well now that i look better the angular velocity is in rad's!
lool forgot that
Thanks.
 

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