Urgent! I\'m doing my quantum mechanics homework and I\'m stuck on part (d) wher

Question

Urgent!

I'm doing my quantum mechanics homework and I'm stuck on part (d) where it asks how does torque affect angular momentum.

What is happening? Especially, in terms of directions. I totally forgot about momentum stuff, and so I'm having trouble.

I think I have figured that currently angular momentum is pointing "upwards right" and torque is directed "into the page". I'm not totally sure though.

HOMEWORK: CLASSICAL ANL QUANTUM SPIN Name QM HW-1 1. Consider a solid spinning sphere of negative charge in a non- uniform magnetic field at instant t, as shown at right (Note you thought briefly about a similar situation during class.) a. Indicate the direction of the magnetic moment of the sphere at instant 1,1 b. Indicate the direction of the angular momentum of the sphere at instant t.How is the angular momentum related to the magnetic moment? c. Determine the direction of the net torque on the sphere at instant t1 (Hint: use the relationship-=-XB.) d. Compare the direction of the net torque with the direction of the angular momentum at instant 11, How does the net torque on an object affect its angular momentum? e. Describe the direction of the angular momentum vector for the sphere at instant /2, a short time after t1. Explain your reasoning f. Describe the direction of the net torque for the sphere at instant t2. Compare the direction of the net torque with the direction of the angular momentum at instant i2 Tutorials in Physics: Quantum Mechanics McDermott, Heron, Shaffer, and P.E.G., U. Wash Winter 201PHYS 225 Preliminary First Edition, 2015

Explanation / Answer

Part (d)

Net torque on an object = I

I = moment of inertia of the object

= angular accleration of the object

but   = d/dt; where = angular velocity

Angular momentum = I

So net torque will change and hence will change angular momentum.

Conversly Torque = Rate of change of angular momentum (as per second law)

        

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