How Do Pendulum and Planetary Motions Compare and Contrast?

[m.l.]

Homework Statement

The motions of a pendulum and a planet undergoing circular motion are compared
a) describe a similarity in their motions
b)describe a difference in their motion
c) Outline a difference in the forces acting on the pendulum and the planet

Homework Equations

The Attempt at a Solution

a) They both have a displacement of 0?
b)one is circular, one is not?
c)?
I'm looking for a more thourough answer.

 

[Dr.D]

a. They are both moving
b. They are doing different things
c. The pendulum is affected by the Earth's gravity while the planet moves under the influence of the sun.

No, wait. Those are probably wrong.

Maybe you should try first.