Calculating Angular Momentum and Torque of a Mass in Freefall

AI Thread Summary
To calculate the angular momentum and torque of a mass in freefall, the object’s linear momentum, p, can be derived from the force of gravity, mg = dp/dt. The angular momentum, L, is determined using the formula L = R × P, where R is the distance vector from the origin to the mass and P is its linear momentum. The net torque, Στ, is related to the change in angular momentum over time, dL/dt. The discussion emphasizes the need to clarify the position vector R and the momentum P for accurate calculations. Understanding these relationships is crucial for solving the problem effectively.
briteliner
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Homework Statement


a mass drops from rest without air resistance, starting from coordinates x=xo, y=yo, z=0. compute its angular momentum about origin at time=t. compare it to the torque on the mass. repeat this, but pick your origin for the angular momentum and torque about the point (x,y,z)=(2xo, 0,0).


Homework Equations


F=dp/dt


The Attempt at a Solution


gravity is the only force so mg=dp/dt. separating and integrating, mgt=p. this is way too simple, how should i attack this problem? i feel that i am not given enough information
 
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\vec L= \vec R\times \vec P

\frac{d\vec L}{dt}=\Sigma \vec \tau

These should straighten things out for you. You found the linear momentum of the object, now find the angular momentum.
 
Last edited:
but how? what is r and what is p with the info i am given?
 
briteliner said:
but how? what is r and what is p with the info i am given?

\vec R is the distance between the object and the point about which you're measuring the angular momentum and torques.

\vec P is the linear momentum of the mass.

\Sigma \vec \tau is the net torque on the mass.

What I posted was the definition of angular momentum, I am surprised you aren't familiar with it.

The second formula relates torque with angular momentum.
 
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