gravitational fields Flashcards
what is a gravitational field
is the region around a body in which other bodies of mass will experience a force.
gravitational field lines
show the shape of the field and the direction of the field
what is the gravitational field strength
at any point in the gravitational field strength is the force acting per unit mass as that point, g=F/m
what type of quantity is gravitational field
vector
are gravitational fields attractive or repulsive
attractive
what happens when we measure the gravitational field strength when we double the distance
will have quarter the strength. inverse square
what is newtons law of gravitation
the relationship between the gravitational force between two bodies is directly proportional to the masses and inversely proportional to the distance.
what is the equation known as newtons law of graviton
F=-GMm/r^2
what is the gravitational constant
G=6.67x10^-11 Nm^2kg^-2
Two masses M and 4M, how does this effect a force
4F
sub in g=f/m into F=-GMm/r^2
g=-GMm/mr^2
g=-GM/r^2
what is the variation of g from the earths surface outwards
g=-GM/(R+h)^2
what is kepler’s third law
states that the square of the period of the planet orbiting the sun is proportional to the mean radius of its orbit cubed: t^2∝r^3
geostationary orbit
is an orbit of the earth made by a satellite that has the same time period and orbital direction as the rotation of the earth.
what is kepler’s laws
- planets travel around the sun in elliptical orbits
- a line joining the sun to a planet will sweep out areas in equal time
- the time period squared to orbit the sun will be proportional to the radius cubed
explain this equation T^2=(4π^2/GM)r^3
F=-GMm/r^2
mv^2/r=GMm/r^2
sub in 2π/T
T^2=(4π^2/GM)r^3
what are geostationary satellites used for
broadcasting
monitoring the weather
monitoring traffic
what is gravitational potential
defined as the work done in moving a mass from infinity
the unit jkg^-1
what is the gravitational potential energy
gpe of a mass in a gravitational field depends on its position in the field.
the escape velocity
escape velocity from a point in a gravitational field is the minimum launch velocity required to move an object from that point to infinity.
variation of gravitational potential with distance for a radial field.
v=-GM/r
how do you work out gravitational potential
v=-GM/r
Calculate the gravitational potential energy
energy=-GMm/r
why is gravitational potential always negative
gravity is an attractive force, moving away from infinity
how can we convert Gravitational potential, to Gravitational Field Strength
by dividing by r, g=v/r
why cant a satellite orbit the south pole
orbit must be equatorial. velocity of spaceship must be parallel to the velocity of a point on the surface of planet.
spaceship must orbit in the same direction as the planet.
