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.

 

[nlightner]

a) Both the pendulum and the planet undergo periodic motion, meaning they repeat the same motion over and over again.
b) The pendulum moves in a back and forth motion in a straight line, while the planet moves in a circular motion. Additionally, the pendulum's motion is due to the force of gravity, while the planet's motion is due to the force of gravity and its own inertia.
c) The pendulum is only acted upon by the force of gravity, while the planet is also influenced by other forces such as centripetal force and the gravitational forces of other objects.