# Gravitational Fields Flashcards Preview

## Physics ALevel OCR > Gravitational Fields > Flashcards

Flashcards in Gravitational Fields Deck (24)
1
Q

Formula for gravitational field strength at a point in a gravitational field

A

g=F/m

2
Q

What are gravitational field lines like on the surface of the earth

A

Uniform

3
Q

What do all gravitational field lines point towards

A

The centre of mass of the the object creating the gravitational field

4
Q

Equation for Newton’s law of gravitation

A

F=-GMm/r^2

5
Q

What is the value and units of G

A

6.67 x 10^-11

Nm^2kg^-2

6
Q

What does the negative sign show in Newton’s law of gravitation

A

That it is an attractive force

7
Q

What is the formula to find gravitational field strength in a radial field

A

g=-GM/r^2

8
Q

Kepler’s first law

A

The orbit of a planet is elliptical with the sun at one of two foci

9
Q

Kepler’s second law

A

Line segment joining the planet and sun will sweep out equal areas during equal intervals of time

10
Q

Keplers third law

A

T^2 is directly proportional to r^3

11
Q

What is the astronomical unit

A

The mean distance between the earth and the sun

12
Q

Equation to find the speed of an object in orbit

A

v^2 = GM/r

13
Q

Equation for the pro oral time period of an object in orbit

A

T^2 =4pi^2r^3/ GM

14
Q

Do keplers laws apply to smaller objects in orbit eg satellites and moons?

A

Yes

15
Q

Sea of satellites

A

Communication, weather, pictures, research

16
Q

3 conditions for a geostationary orbit

A
• be in orbit above the equator
• orbital period of 24 hours
• rotate same direction as earth
17
Q

Symbol of gravitational potential

A

Vg

18
Q

What is Vg defined as?

A

The work done per unit mass to move an object to that point from infinity

19
Q

Is gravitational potential scalar or vector

A

Scalar

20
Q

Equation for gravitational potential

A

Vg= -GM/r

21
Q

Why is Vg always negative

A

Work is done to move one object away from another. Vg at infinity is a maximum of 0, so all values is negative as work is done to move it away from that point

22
Q

Equation for gravitational potential energy in a uniform gravitational field

A

Ep=mgh

23
Q

Equation for gravitational potential energy in a radial field

A

E=mVg

24
Q

Equation for escape velocity

A

v^2=2GM/r