Gravitational fields

Question 1

how do you find the acceleration due to gravity

Answer 1

measure mass
measure reading on newtonmeter
f=ma
graph should intercept origin
force on y mass on x gradient should be acceleration

Question 2

what is the value for G

Answer 2

G = 6.67 x10^-11 m^3kg^-1s^-2

Question 3

when would you not uses Egp = Ke

Answer 3

When there is a big change of height due to the effect of gravity is different the further away you are

Question 4

whats the Force (w) equation

Answer 4

Fw = - Gmamb
————-
r^2

Question 5

equation for effect due to gravity

Answer 5

follows the inverse square law
g=Gm
——
r^2

Question 6

Definition for Gravitational Potential

Answer 6

**The gravitational potential energy (G.P.E) is the potential energy an object has when lifted off the ground **

V is the GPE per unit mass in a gravitational field
V = Egp
——
m
Therefore the Gravitaional potential at a position in a field caused by mass B would be
Vb = - Gmb
———
r

Question 7

simplified potential equation

Answer 7

V = - Gm
——–
r

Question 8

What equation relates Gravitational Potential and velocity

Answer 8

V1 - V2 = 1/2 x v^2

Question 9

simularities of gravitational fields and electric fields

Answer 9

1. both fields follow the inverse square law
   ( inversely proportional to the square distance away(r))
   2.both can be radial and uniform fields
2. both have infinite range

Question 10

Differences of Gravitational fields and electrical fields

Answer 10

1.Gravitational fields only cause attraction where as electric fields both attract and repel
2.gravitational fields only act on objects with mass where as electric fields only act on charged particles
3.Gravitational potential is always negative where as electric potential can be either positive or negative
4. the force between charges at a given separation is much stronger than the force between masses at the same separation

Question 11

what is keplers Third Law

Answer 11

The square of an orbiterd period, T, is proportional to the cube of its seperation from what is orbiting , r.
It is also stated that the square of the period, T, is inversely proportional to the mass being orbited

Question 12

equations for centripetal forces

Answer 12

f = mv^2
——-
r
f = gmamb
———-
r^2

Question 13

velocity in terms of mass

Answer 13

Gm
—— = v^2
r

Question 14

state the defining equation for newtons law of gravitation

Answer 14

F = - GM
/ ———
r^2

Question 15

what does newtons law of gravitation state mean

Answer 15

The gravitational force between two masses is proportional to the product of their masses and is inversely proportional to the square of the seperation of their centres

Question 16

what is gravitational field strength? and the unit

Answer 16

the force per unit mass felt by the object
Nkg^-1

Question 17

what is gravitational potential at a point?

Answer 17

The energy transferred per unit mass when moving an object from infinity to that point

Question 18

state the equation for gravitational potential

Answer 18

V = -GM
——–
r

Question 19

what is an equipotential

Answer 19

a plane in which all points have the same potential

Question 20

what is true when a mass moves along an equipotential

Answer 20

no work is done when moving along an equipotential

Question 21

what does the area under a force-seperation graph represent

Answer 21

energy

Question 22

what do field lines tell you

Answer 22

the direction of the arrows show the direction of the field. the strength of the field is represented by the density of the field lines

Question 23

what is gravitational potential

Answer 23

the potential energy per unit mass, at any point in the field. Zero potential is defined at infinity, hence at a point close to a mass toe potential of an object would be negative

Question 24

work done by moving a mass in a field

Answer 24

work done = mass x change in gravitational potential

Question 25

what is gravitational potential difference

Answer 25

Gravitational potential difference is the difference in the gravitational potentials of two points in a gravitational field

Question 26

how much work is done per unit distance when you move along an equipotential ?

Answer 26

No work is done when moving across equipotentials, as the potential at each point is the same

Question 27

why is gravitational potential a negative value?

Answer 27

work needs to be done to move an object from the inside the field to outside the field. since outside the fields potential is defined as zero then the potential inside the field must be negative

Question 28

how is the orbital period related to the radius of a circular orbit

Answer 28

T^2 is proportional R^3

Question 29

compare the Potential energy and Kinetic energy of a lower orbit and a higher orbit

Answer 29

A lower orbit (smaller m) has less potential energy and more kinetic energy than a higher orbit (bigger r)

Question 30

what type of matter is affected by a gravitational field?

Answer 30

Any object or matter with mass will experience an attractive force.

Question 31

what is the relationship between the field strength and the field lines that represent it ?

Answer 31

the closer the lines are together, the stronger the gravitational field strength. The further apart the lines are, the weaker the field strength.

Question 32

what is a point mass?

Answer 32

A point mass is a theoretical object that has a mass but no dimensions. This means that all of its mass acts at a single point

Question 33

what is the cheat equation for the velocity using gravitational potential

Answer 33

V1 - V2 = 1/2 x v^2
-Gmb -Gmb
——— - ——– =1/2 v^2
r1 r2