Table of Contents

Kick Off Questions

The Newtonian Gravitational force acting on object 1 caused by object 2 is given by: $$\vec{F}_{grav} = -G\dfrac{m_1 m_2}{|\vec{r}|^2}\hat{r}$$

  1. What is $\vec{r}$? Draw this.
  2. What is the direction of $\vec{F}_{grav}$?
  3. If an object is moving in a circle with constant speed, is there a non-zero net force? If there is a non-zero net force, what is its direction?

Project 3: Learning goals

  • Predict the motion of a system of gravitationally interacting objects analytically and computationally.
  • Evaluate the validity of predictions for the motion of gravitationally interacting objects.
  • Generate free body diagrams for a system of multiple objects and identify Newton’s 3rd Law force pairs in order to explain physical phenomena.
  • Determine the net force acting on a single-particle system using a diagrammatic representation (free-body diagram) and by performing any necessary calculations.
  • Explain the motion of single-particle systems using interactions (forces) as the basis for the explanation.

Project 3: Learning Concepts

  • Forces cause changes in momentum
  • Uniform circular motion
  • Newtonian gravitational force

Project 3: Part A: Geostationary orbit

The Carver Media Group is planning the launch of a new communications satellite. Elliot Carver (head of Carver Media Group) is concerned about the launch. This is a $200,000,000 endeavor. In particular, he is worried about the orbital speed necessary to maintain the satellite's geostationary orbit (and if that depends on the launch mass). You were hired as an engineer on the launch team. Carver has asked that you allay his concerns.

Conceptual questions to be answered AFTER completing part A:

  1. How do you know you can classify the satellite's orbit as uniform circular motion?
  2. If the gravitational force is acting inward, why does the satellite not fall to Earth?
  3. What is the difference between the gravitational force, the net force, and the centripetal force ($mv^2/r$) in this case?
  4. Is there a force exerted on Earth? If so, why do we ignore it? If not, why not?
  5. Explain the difference between mass and weight.

Project 3: Part B: Geostationary orbit

On a single graph, plot both the x-component of the satellite's momentum and the x-component of the net force acting on the satellite.