Download - Chapter 13
The Universal GravityThe gravitational attraction of two objects of m1 and m2 is given by (magnitude only):
ExampleFind the gravitational force between two people of mass m=70kg, r =0.5m away from each other.
ExampleIf your weight on Earth is WE. What will your weight on the surface of a mysterious Planet X given RX = 20 RE and MX = 300 ME.
SatelliteFind the period and tangential velocity of a satellite of mass m at distance r from the center of the Earth.
Conservation of (Total) EnergyTotal energy is always conserved. We will be dealing with only two kinds of energy, kinetic energy and potential energy.
Gravitational Potential Energy
What about PEG = mgh?
PEG = mgh is only true near the planet’s surface. Far away the gravitational field gets weak and PEG = mgh is no longer true.
Conservation of energyA rocket is launched vertically upward at v0= 2.1km/s. How high can it go?
What is the initial KE and PE?
If it reaches radial distance r, what is the final KE and PE?
Conservation of EnergyHow fast must the launch speed be for the rocket to reach a height above the earth equal to RE.
Shoot highHow fast must the launch speed be for the rocket to reach a height above the earth equal to RE.
What you have learned
• Universal gravity• Gravitation potential energy• Orbital motion• Escape velocity