A particle is acted on by two torques about the origin: T1 has a magnitude of 4.3 N*m and is directed in the positive direction of the x axis, and T2 has a magnitude of 3.2 N*m and is directed in the negative direction of the y axis. What are the magnitude [in N*m] and direction [counterclockwise from the +x axis] of dL/dt, where L is the angular momentum of the particle about the origin?
.. is there an equation that finds the magnitude of the net torques? help?
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* Physics - Torque - bobpursley, Saturday, March 31, 2007 at 8:46am
Add the torques as vectors.
T=I * angular acceleration is a VECTOR equation, as is
angularmomentum=I * angularvelocity
angular veloicty= wo + angacceleration*time
is also a vector equation. So add the vectors for T, solve for angacceleration, then solve for angular momentum.
Now on directions. When one indicates direction on a circular torque, or velocity, as in this case , use the right hand rule. Your stating the T1 is in the direction of x means it is rotating in the YZ plane, from Y to Z. I hope this is what you meant in the problem description.
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So for Torque the net Torque is:
Tnet = (4.3 N*m)i - (3.2 N*m)j
T = I*angular acceleration
How do I calculate Inertia if I am not given a mass of the particle?
Actually you cant. You need to know the mass of the particle, AND its location in relation to the origin. THe statement did not mention either.
I have read the problem several times, and I can surmise what it meant on that mass, or location. Perhaps it meant a point charge M, at the origin, but perhaps again not.
I agree, it has me baffled.
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