Gravity and Orbits Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Describe the orbits of moons.

A

Slightly elliptical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the orbits of planets.

A

Slightly elliptical

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the orbits of comets.

A

Very elliptical with the Sun at one focus (near one end of the orbit).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Why does a comet travel faster when its nearer the Sun?

A

Because the increased pull of gravity makes it speed up the closer it gets to the Sun.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is a geostationary satellite?

A

An artificial satellite with orbital period of exactly one day.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do you calculate speed of an orbit?

A

speed = distance/time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do you calculate circular orbit speed?

A

Distance = circumference
so 2 x pi x r (r being the distance from the centre of the object you are orbiting)
So
v = 2 x pi x r /T
T measures in sec
CHECK UNITS in the question and convert before you calculate.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Why are geostationary satellites useful?

A

These are useful in communications because they are always over the same part of the planet.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe the change in orbital speed of a comet.

A

A comet travels much faster when it is nearer the Sun than it does in the more distant parts of its orbit.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q
A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

The structure of the Solar System is determined by …

A

…Orbits - the paths that objects take as they move around each other in space.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe the path that planets move around the Sun.

A

Almost circular orbits.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

If an object is travelling in a circle…..

A

…. it is constantly changing direction (and so constantly accelerating), which means there is a force acting on it. (F=ma)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the name of the force causing the object to travel in a circle?

A

Centripetal force (acting towards the centre of the circle).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why doesn’t the object just fall towards the centre of what it is orbiting?

A

Because the object is already moving, so it just causes it to change direction.
The object keeps accelerating towards what its orbiting but the instantaneous velocity (which is at right angle to the acceleration) keeps it travelling in a circle.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What force keeps the planets and comets in their orbits around the Sun?

A

Gravitational force. The gravitational attraction of the Sun keeps them in orbits around it.

17
Q

How are satellites kept in their orbits around planets?

A

By the gravitational attraction of the planet they are orbiting.

18
Q

What happens to the gravitational field strength (g) as the mass increases?

A

The larger the mass of the body creating the field, the stronger the gravitational field strength.

19
Q

Why does an object weigh more on Earth than the Moon?

A

The Earth is more massive than the Moon, so an object would weigh more on Earth than it would on the Moon. This is because the gravitational field strength is larger on Earth than the Moon due to the mass of the Earth being larger.

20
Q

What variables affect gravitational field strength?

A
  1. The mass of the body creating the field.
  2. The distance from the body creating the field.
21
Q

The closer you get to a star or planet…..

A

…. the stronger the gravitational force is.

22
Q

How does the strength of the gravitational force affect the instantaneous velocity?

A

The stronger the force, the larger the instantaneous velocity needed to balance it. So the closer you get to the star or planet, the faster you need to travel to remain in orbit.

23
Q

In a stable orbit, if the speed of the object changes….

A

… the size (radius) of its orbit must do too.
Faster moving objects will move in a stable orbit with a smaller radius than slower moving ones.

24
Q

Calculate the speed m/s of a satellite that is orbiting above the Earth’s surfaces at an altitude of 600 km. The radius of the Earth is 6400 km and the satellite takes 200 min to orbit the Earth once.

A