Physics Conceptual Problem?

mitch

Once released, a pendulum swings back and forth in a state of simple harmonic motion.

Ignoring any drag or friction effects, which of these statements about the motion of the

pendulum is true?

a) The energy, linear and angular momentum are conserved.

b) The energy and linear momentum are conserved, but not angular momentum.

c) The energy and angular momentum are conserved, but not linear momentum.

d) The energy is conserved, but not angular or linear momentum.

e) Nothing is conserved.

I believe that linear momentum is not conserved but I'm not sure about angular momentum. Can anyone help me understand?

ncs

There are external forces applied, and so momentum is not conserved. The only valid answer is "d."

That angular momentum is not conserved should be obvious -- the moment of inertia is constant, but the angular velocity is not.

Hope this helps!