Gravitational fields Flashcards
What is gravitational force?
It if the gravitational force per unit mass.
Describe a gravitational field.
For an isolated point mass, the gravitational field is spherical in shape with the mass at the centre.
What is a field line and what is its relationship to a gravitational field?
A field line is a path followed by a unit mass in that gravitational field.
The higher the density of field lines there is, the more stronger the gravitational field is.
What is Newton’s law of gravitation?
The gravitational force between two point masses is proportional to the product of the masses and inversely proportional to the square of their separation.
F = GMm/r2
What is the nature of a gravitational field?
The Gravitational force between two masses is independent of the medium separating the mass and is always an attractive force.
What is gravitational field strength?
The gravitational field strength at a certain point is the gravitational force exerted per unit mass.
What are the formula and the derivation of gravitational field strength?
Relate W = mg and Newton’s law of gravitation.
What is the gravitational potential at a point?
It is the work done in bringing a point mass from infinity to a certain point
What is the formula for gravitational potential?
Ø = -GM/r
Why is there a negative sign in the equation for gravitational potential?
- Gravitational force is always attractive
- Gravitational potential decreases to zero at infinity
- Gravitational potential decreases in the direction of a field.
What is gravitational potential energy?
The gravitational potential energy of a mass m in the gravitational field of a mass M is the work done in bringing the mass m from infinity to that point.
What is the formula for gravitational potential energy?
What are the characteristics of a geostationary orbit?
- Equatorial orbit
- Period is 24 hours - it has the same angular velocity as earth
- From west to east - Same direction of the rotation of earth.
What is a geostationary satellite?
It is one where it always appears to be above a certain position on the earth.
The time period is 24 hours and the orbital radius is a fixed value from the centre of the earth.
The mass is not fixed so GPE and EK are different values.
Describe the launching of a geostationary satellite.
It is launched from the equator of the earth, from west to east, in the direction of the earth such that the axis of rotation of the satellite and the rotation of the earth will coincide.
How is escape velocity derived?
By using conservation of energy.
