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The physics of orbital motion - Coggle Diagram
The physics of orbital motion
velocity is a
vector quantity
(speed + direction)
if the speed/direction changes, there is a change in velocity (
acceleration
)
to keep a body moving in a circle there must be a force (gravity) directing it towards the centre + holding it in orbit
gravity pulls the object in a curved path, creating a
centripetal force
, producing the continuous change in direction of circular motion
Even though the
speed may be constant
, the object is
constantly accelerating
because the
direction (i.e. velocity) is constantly changing
via the circular path
this unbalanced force results in acceleration towards the centre
To keep an object in a stable orbit (moving at constant speed) → the faster it moves/the smaller the orbital radius, the greater the gravitational force needed
If the speed of an orbiting object changes the orbital radius must also change
If an orbiting object initially slows down, it's pulled by the gravitational centripetal force into an orbit of smaller radius and increases in speed
If an object initially speeds up, it partially overcomes the centripetal gravitational force moves to a higher orbit of greater radius, but then it slows down in a larger radius stable orbit.
the objects are moving through empty space (
vacuum
), so there are no forces of friction to slow the object down
the further the planet is for the Sun (our star) the longer it takes for that planet to orbit the Sun once
thus, the slower it moves and the larger the radius of its orbit
the gravitational field strength depends on the mass of the object creating the field
also varies with its distance from the object its orbiting (the closer it is, the stronger the force)
the stronger the force, the faster the object must move in order to avoid crashing into the object it's orbitting
the larger the mass of the object, the stronger the gravitational field
the stronger the force an orbiting object experiences, the greater the instantaneous velocity needed to balance it e.g. to keep it in stable orbit
the closer an object to what it's orbitting, (i.e. the smaller its orbital radius), the faster the orbiting object must travel to stay in orbit
gravitational attraction to sun increases
To have a stable orbit, the object must have a speed that matches the radius of the orbit
for an object undergoing circular motion...
the acceleration doesn't change its speed
the acceleration causes the object to change direction
the velocity changes but the speed is the same
the instantaneous velocity is perpendicular to the centripetal force
change in speed causes change/failure in orbit
for a stable orbit, the greater the radius, the slower the speed
an object will only accelerate if a
resultant force
is acting on it (that being centripetal force)
Paths with a different orbital radius lead to a different orbital velocity
orbital speed: speed = circumference / time period
factors that determine the centripetal force of an object
mass of the object
speed/velocity of the object
radius of the orbit of the object