12: The Gravitational Field

Question 1

What is angular velocity?

Answer 1

The angle the object rotates through per second

Question 2

Why is a car travelling at constant speed in a circle, accelerating?

Answer 2

It’s velocity is changing since its direction is changing

And acceleration = rate of change of velocity

Question 3

In which direction is a car travelling in a circle, accelerating?

Answer 3

Centripetal acceleration is always directed towards the centre of the circle

Question 4

What produces the centripetal acceleration?

Answer 4

Centripetal force

Question 5

In which direction does centripetal force act?

Answer 5

Towards the centre of the circle

Question 6

What is a gravitational field?

Answer 6

A region where an object will experience a non-contact force

Question 7

What does an object experience when you put it in a gravitational field of another object?

Answer 7

Experience an attractive force

Question 8

What are gravitational field lines?

Answer 8

Arrows showing the direction of the force that masses would feel in a gravitational field

Question 9

What is a uniform field? How can you identify a uniform field with field lines?

Answer 9

A field that is the same everywhere. This is shown by the field line being equally spaced and going in the same direction

Question 10

Point masses have a [ ] field

Point masses = ….

Answer 10

Radial

A mass where its assumed they act as if all there mass in concentrated at their centre

Question 11

As a mass gets further from earth, what happens to the strength of the force it experiences? How is that represented in field lines?

Answer 11

Further - force decreases

Lines of force are further apart

Question 12

Why does a small mass in earth’s gravitational field not affect earth much?

Answer 12

Earth is so much more massive

Question 13

What can you assume about the gravitational field at the surface of Earth? How is this represented in field lines?

Answer 13

Assume it is perfectly uniform

So the field lines are parallel and equally spaced

Question 14

The force experienced by an object in a gravitational field is always [ ]

Answer 14

Attractive

Question 15

What is gravitational field strength?

Answer 15

Force per unit mass

Question 16

A mass in a uniform gravitational field experiences a [ ] force

Answer 16

constant - because g will be the same everywhere

Question 17

When is ΔEɢᵣₐᵥ positive? Negative?

Answer 17

Positive: When the height increases
Neg: When the height decreases

Question 18

What is the principle of conservation of energy?

Answer 18

Energy cannot be created or destroyed. Energy can be transferred from one form to another but the total amount of energy in a closed system will not change

Question 19

You [ ] gravitational potential energy if you move away from the Earth

Answer 19

Gain

Question 20

Egrav is always positive/negative

Answer 20

Negative (always attractive)

Question 21

Egrav = Δs * [ ]

Answer 21

F grav

Question 22

What is gravitational potential?

Answer 22

Potential energy per unit mass

Question 23

What do equipotentials show?

Answer 23

All the point in a field which have the same potential

Question 24

If you travel along a line of equipotential you don’t lose or gain [ ]

Answer 24

Energy - no work is done

Question 25

What shape are the equipotentials around a uniform spherical mass?

Answer 25

Spherical surfaces

Question 26

Equipotentials and field lines are parallel/perpendicular

Answer 26

Perpendicular

Question 27

What is a satellite?

Answer 27

A small mass that orbits a much larger mass

Question 28

When something is in orbit, which 2 forces must be equal?

Answer 28

Centripetal force and gravitational force

mv²/r = GmM/r²