# Chapter 7: Circular Motion and Gravitation

Circular Motion

Using circus trick-riders as an example, this video describes how centripetal acceleration works.

http://www.pbs.org/opb/circus/classroom/circus-physics/centripetal-acceleration/

(Objective: Explain how the apparent existence of an outward force in circular motion can be explained as inertia resisting the centripetal force.)

This simple experiment can be done with materials on hand and nicely illustrates the concept of centripetal force.

http://people.umass.edu/plecprep/mech/1d5040.html

(Objective: Explain how the apparent existence of an outward force in circular motion can be explained as inertia resisting the centripetal force.)

Newton’s Law of Universal Gravitation

Use this simulation to manipulate the positions of objects in space and alter their orbits.

(Objective: Explain how Newton’s law of universal gravitation accounts for various phenomena, including satellite and planetary orbits, falling objects, and the tides.)

An interactive simulation that takes the viewer on a journey to a black hole. Included are an encyclopedia of black holes facts and several applets.

http://hubblesite.org/explore_astronomy/black_holes/

(Objective: Apply Newton’s law of universal gravitation to solve problems.)

Motion in Space

A short history of Kepler’s work and description of his three laws.

http://projects.astro.illinois.edu/data/KeplersLaws/

(Objective: Describe Kepler’s laws of planetary motion.)

Weight and Weightlessness. A one- and two-player basketball game illustrating free fall and gravitational force.

http://www.nasa.gov/audience/foreducators/microgravity/home/free_fall_ball.html

(Objective: Relate Newton’s mathematical analysis of gravitational force to the elliptical planetary orbits proposed by Kepler.)

Simple Machines

With the help of a design team that included some staffers from the NASA Jet Propulsion Lab, the band OK Go constructed an enormous Rube Goldberg machine for a music video. In this video, watch this simple yet intricate machine complete its task.

http://blogs.nasa.gov/cm/blog/whatonearth/posts/post_1275422073165.html

(Objective: Identify the six types of simple machines.)