21 Gravitational Fields Flashcards
Gravitational potential energy Ep
At a point in a gravitational field is the work done to move a small object from infinity to that point. The change of gradational potential energy of a mass (m) moved through a height (h) near the Earths surface ΔEp = mgΔh
Gravitational potential v
At a point in a gravitational field is the work done per unit mass to move a small object from infinity to the point. At the distance r from the centre of a spherical object of mass (M).
V= -GM/r
(a point is the work done per unit mass to move a small object from infinity to that point)
zero value at infinity
Equipotential
A line or surface in the field along which the electric or gravitational potential is constant
(no work is done when moving along a equipotential surfaces )
Gravitational fields strength, g
Force per unit mass on a small mass placed in the field
g = F/m ( gravitational force on a small mass)
Distance r from a point mass (M).
g= GM/r^2
radial field
a field in which the field lines are straight and converge or diverge as if from a single point
field line (line of force)
direction of a field line indicates the direction of the force. an electric field line is the path followed by a free positive test charge. the gravitational field line of a single mass point towards that mass
uniform gravitational field
The earth is uniform over a region which is small compared to the scale of the Earth
potential gradient
at a point in a field is the change of potential per unit charge of distance along a field line at that point.
potential gradient = - the field strength at any point
keeper’s third law
for any planet, the cube of its mean radius of orbit is directly proportional to the square of its time period
R^3 / T^2 = GM/ 4(pi)^2
newton’s law of gravitation
the gravitational force F between two point masses M and m at distance r apart
F= GMm/ r^2
escape velocity
the minimum velocity an object must be given to escape. from the planet when projected vertically from the surface
gravitational field (g) a vector?
yes its a vector
Gravitational Force is a ______ force
attractive force
Gravitational fields
a region within which an object experience gravitational force
the closer the lines the stronger the field
field strength decreases as the distance from the object increases
g= F/M
r is measured from the ____
centre
