Chapter 11 - Out into Space Flashcards Preview

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Flashcards in Chapter 11 - Out into Space Deck (16)
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1
Q

Kepler’s Laws

A
  1. Orbits are ellipses with the sun at one focus. 2. Line from the sun to a planet sweeps out equal areas in equal times. 3. Time period and radius of orbit related by: T^2 is proportional to r^3
2
Q

What is a point mass?

A

Objects that behave as if all their mass is concentrated in the centre.

3
Q

What is the gravitational field strength?

A

Force per unit mass given by the equation F = mg thus g = F/m

4
Q

Equation for gravitational field strength

A

g = - GM/r^2

5
Q

What is gravitational potential energy?

A

The work that would need to be done to move a mass against the force of gravity.

6
Q

Key points about GPE graph

A
  1. Mass on earth’s surface has negative GPE. 2. As you move a mass away from the earth it gains GPE. 3. GPE is 0 at an infinite distance away from Earth. 4. Force is greatest at Earth’s surface where tangent to graph is steepest.
7
Q

What is gravitational potential?

A

Potential energy per unit mass.

8
Q

Centripetal force = gravitational force rearrangement

A

v = root(GM/r)

9
Q

What is a standard candle?

A

An object that you can measure the brightness of directly. E.g cepheid variable stars: their brightness changes in a certain pattern. thus finding such a star in a galaxy can allow you to determine the distance of the galaxy from us.

10
Q

What is 1 AU

A

Mean distance between the Earth and the Sun.

11
Q

Describe the field lines of the gravitational field close to the surface of the Earth

A

Gravitational field is almost uniform - field lines are almost parallel and may be assumed that field is perfectly uniform.

12
Q

velocity of a geostationary orbit

A

V = (2pi r)/T v = r w

13
Q

What must be done to put a satellite into a circular orbit around the earth?

A

Balance the centripetal and gravitational forces. mv^2/r = GMm/r^2 Therefore v = root(GM/r) or v = root(gr) since gr = GMr/r^2

14
Q

Inside a sphere of uniform mass, describe the relationship between the gravitational force and the distance of an object from the centre of a sphere.

A

Gravitational force is directly proportional to the distance of an object from the centre of the sphere.

15
Q

What must be done to completely leave the orbit of the earth?

A

Convert KE to PE.

1/2 mv2 = GMm/r

Rearrange to find v = root(2GM/r)

16
Q
A