3.7.2 Gravitational fields Flashcards
What is a force field?
A region of space where an object will experience a non-contact force
What is a non-contact force?
A force that acts without physical contact
What type of object experiences a gravitational force?
An object with mass
What is a gravitational force field?
A region of space where a mass experiences a force due to the gravitational attraction of another mass
What are the properties of gravitational fields?
They cannot be repulsive - so always attractive.
They have infinite range
There is a greater gravitational force around objects with large mass.
What is the gravitational field strength formula for a uniform field?
g=F/m
What are the factors that affect the gravitational field strength at the surface of a planet?
The radius or diameter
The mass/density of the planet
What do gravitational field lines look like?
Around a point mass - radial lines (non unform)
Uniform field - equidistant parallel lines
What is point mass approximation?
For a point outside a uniform sphere, the sphere’s mass can be considered to be a point mass at its centre - where its mass is distributed evenly. The gravitational field lines around a uniform sphere are identical to the ones around a point mass.
Point mass definition
A body covers a very large distance as compared to its size, so, to study its motion, its size or dimensions can be neglected.
State 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.
What is Newton’s Law of Gravitation as a formula?
F_g=G(m_1*m_2)/r^2
What is the formula for gravitational field strength around a radial field?
g=GM/r^2
What is the gpe on the surface of the Earth?
0
What is the definition of gpe outside of the Earth’s surface?
The energy an object possesses due to its position in a gravitational field
What is the definition of gpe at a point?
The work done per unit mass in bringing a test mass from infinity to a defined point
What is gpe at infinity?
0
What is the formula for gravitational potential difference?
deltaV= V_f - V_i
What is the formula for gravitational potential?
V= -GM/r
it is a scalar quantity and negative because work is done to move a mass away from a planet, so gets less negative.
What is the gradient of a potential-distance graph?
-g
What is the formula for work done on a mass?
deltaW=mdeltaV
What is the formula for change in gpe?
deltaGPE=GMm(1/r_1-1/r_2)
What is an equipotential surface?
When a line is drawn through field lines, all the points on that line have the same potential difference. No work is done when moving along an equipotential surface
