Day 1 - Orbits

What is an orbit?

An orbit is the path of an object falling forever toward another without impacting, maintaining a balance of kinetic and potential energy.

What did Douglas Adams mean by 'learning how to throw yourself at the ground and miss'?

It suggests the complexity involved in achieving orbit, where the object must fall toward the Earth but misses due to its tangential velocity.

What are the conditions for Newton's cannonball concept?

If an object is too slow, it will impact the Earth; if too fast, it will escape; there is a specific velocity that maintains a constant distance from the Earth.

What is the orbital velocity at treetop according to the lecture?

The orbital velocity at treetop is approximately 8 km/s.

What did Newton’s Universal Law of Gravitation state?

All bodies attract each other proportionally to the product of their masses and inversely to the square of the distance between them.

What is the formula for Newton's Universal Law of Gravitation?

F = GMm/r² where F is the force, G is the gravitational constant, M and m are the masses of the objects, and r is the distance between their centers.

What does it mean when it's stated 'outside the radius of the body, it appears as a point mass'?

It means that for an observer outside a spherical body, the gravitational effects of the body can be treated as if all its mass is concentrated at a single point at its center.

What is centripetal force in the context of orbits?

Centripetal force is the force that keeps a satellite in orbit, described by the formula Fc = mv²/r, where m is the mass of the satellite, v is the tangential velocity, and r is the distance from the center of the Earth.

What is the relationship between mass and orbital velocity?

Orbital velocity is only dependent on the primary body's mass and the distance from its center, expressed as v = (GM/r)^(1/2).

How was the mass of the Earth estimated?

The mass of the Earth was estimated using the distance from the Earth to the Moon and the known angular rate of the Moon's orbit.

What is the formula to calculate the mass of a body using orbital velocity?

M = V²*r/G, where M is the mass, V is the orbital velocity, r is the distance to the center of the mass, and G is the gravitational constant.