12: The Gravitational Field Flashcards
What is angular velocity?
The angle the object rotates through per second
Why is a car travelling at constant speed in a circle, accelerating?
It’s velocity is changing since its direction is changing
And acceleration = rate of change of velocity
In which direction is a car travelling in a circle, accelerating?
Centripetal acceleration is always directed towards the centre of the circle
What produces the centripetal acceleration?
Centripetal force
In which direction does centripetal force act?
Towards the centre of the circle
What is a gravitational field?
A region where an object will experience a non-contact force
What does an object experience when you put it in a gravitational field of another object?
Experience an attractive force
What are gravitational field lines?
Arrows showing the direction of the force that masses would feel in a gravitational field
What is a uniform field? How can you identify a uniform field with field lines?
A field that is the same everywhere. This is shown by the field line being equally spaced and going in the same direction
Point masses have a [ ] field
Point masses = ….
Radial
A mass where its assumed they act as if all there mass in concentrated at their centre
As a mass gets further from earth, what happens to the strength of the force it experiences? How is that represented in field lines?
Further - force decreases
Lines of force are further apart
Why does a small mass in earth’s gravitational field not affect earth much?
Earth is so much more massive
What can you assume about the gravitational field at the surface of Earth? How is this represented in field lines?
Assume it is perfectly uniform
So the field lines are parallel and equally spaced
The force experienced by an object in a gravitational field is always [ ]
Attractive
What is gravitational field strength?
Force per unit mass
A mass in a uniform gravitational field experiences a [ ] force
constant - because g will be the same everywhere
When is ΔEɢᵣₐᵥ positive? Negative?
Positive: When the height increases
Neg: When the height decreases
What is the principle of conservation of energy?
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
You [ ] gravitational potential energy if you move away from the Earth
Gain
Egrav is always positive/negative
Negative (always attractive)
Egrav = Δs * [ ]
F grav
What is gravitational potential?
Potential energy per unit mass
What do equipotentials show?
All the point in a field which have the same potential
If you travel along a line of equipotential you don’t lose or gain [ ]
Energy - no work is done
What shape are the equipotentials around a uniform spherical mass?
Spherical surfaces
Equipotentials and field lines are parallel/perpendicular
Perpendicular
What is a satellite?
A small mass that orbits a much larger mass
When something is in orbit, which 2 forces must be equal?
Centripetal force and gravitational force
mv²/r = GmM/r²
