Gravitational Field Flashcards
Newton’s Law of Gravitation?
The gravitational force of attraction between two point masses is proportional to the product of their masses and inversely proportional to the square of their separation.
F= (GMm/R^2)
Gravitational Field Strength?
Gravitational Force per unit mass at that point, g= F/m
Field strength due to point mass M?
g= GM/r^2
What is gravitational Potential
Work Done in bringing a unit mass from infinity to that point without a change in its KE, = W/m
Why potential values are negative?
Potential at infinity is zero, and gravitational force is attractive, so work done in bringing unit mass from infinity is negative. Potential is work done per unit mass, so always negative
Gravitatational Potential due to point mass?
- (GM)/ r
Relationship betwen field strength and potential
Field strength is the -gradient of potential distance graph
What is gravitational potential energy?
GPE of any mass at a point in gravitational field of another mass is the work done in bringing that mass from infinity to that point, U = -(GMm)/r
Total energy of satellite
-(GMm)/2r
Formula for escape speed?
v= squareroot (2gR) = squareroot (2GM/R)
Formula for satellite in circular orbit?
GMm/r^2 = mv^2/r , mrw^2= mr(2pi/T)^2
Why satellite does not move in direction of g force?
The gravitational force exerted by the Earth is just sufficident to cause the centripetal acceleration.
What is geostationary satellite?
One which is always above a certain point on Earth as Earth rotates about its axis
Conditions for geostationary satellite?
Lie in equatorial plane of earth, rotate from west to east and with a period of 24 hours
Why geostationary orbit must lie in equatorial plane?
Since the force of attraction to the Earth is to its centre, the circular orbit must be centered on the centre. The plane of orbit must lie in the equator, otherwise the period would not be 24 hours anymore.
