An object moves in a straight line if
Net force on it acts in the direction of motion or net force is 0
Uniform circular motion
Object that moves in a circle at constant speed
Centripetal accleration
Acceleration that points towards the center of a circle
The greater the speed, the _____ the velocity changes direction.
Faster
Acceleration vector is always perpendicular to the velocity vector which is ________ to the circle
Tangent
Frequency
Number of revolutions per second
Period
Time required for one complete revolution
An object moving in a circle must have a _____ applied to it to keep it moving in a circle
Force
- Newton's 2nd law
If an object is in uniform circular motion and is accelerating, then ______
The net force must be directed towards the center of the cirlce
Automobile rounds a curve example
Person tends to move in a straight line but the car seat (friction) or the door of the car (contact force) exerts a force on you. The car also has a force exerted on it toward the center of the curve which is the frictional force between the tires and pavement
When the speed of an object changes, the force acting on it has a ________ component
Tangential
What exerts the force of gravity?
Earth exerts the gravitational force on objects at its surface
The gravitational force exerted by the earth on any object decreases with the square of its distance r from the earth's center relationship
Force of gravity is inversely proportional to the distance squared
Newton's law of graviation
Every particle in the universe attracts every other particle with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them. This force acts along the line joining the 2 particles.
Centripetal force requirement
Inward force acting on an object in order for it to have an inward accleration
Centripetal force in horizontal circle on a string
Tension horizontal component
Centripetal force at minimum velocity required for the string to maintain necessary tension
Force of gravity
Centripetal force for a vertical circle on a string when the ball is moving greater than minimum speed
Tension force
Centripetal force in a vertical circle on a string when ball is at the bottom
Tension force- gravity force
Centripetal force when a Person riding the loop the loop roller coaster
Tension force+gravity force
Centripetal force when satellite is orbiting earth
Earths gravity
Centripetal force when a car is rounding a corner on a level road
Frictional force between the tires and pavement
Centripetal force when a car is rounding a curve on a frictionless surface
Horizontal component of normal force
Orbital speed increases when orbital ________
Radius decreases
Tangential speed is proportional to ________
Distance from the axes of rotation
Apparent weightlessness
When an object seems "weightless" because there is no contact force to make one feel the weight and it is free falling
Kepler's first law
The path of each planet about the sun is an ellipse with the sun at one focus
Ellipse
Closed curve such that the sun of the distances from any point P on the curve to two fixed points(foci F1 and F2) remains constant.
F1P+ F2P is the same for all points on the curve
Kepler's second law
Each planet moves so that an imaginary line drawn from the sun to the planet sweeps out equal areas in equal periods of time.
Relationship between distance and time for Kepler's second law
Smaller area, moving slower because the distance is farther away from earth and vice versa
Kepler's third law
The ratio of the squares of the period T of any 2 planets revolving about the sun is equal to the ratio of the cubes of their mean distances s from the Sun.
Kepler third law equation
(T1/T2)^2=(s1/s2)^3
Kepler's third law only applies ______
To objects orbiting the same attracting center.
Ex. Cannot compare moon orbit around earth to Mars or it around the sun
Gravitational potential energy is calculated relative to _____
A central body (earth)
Relationship between r (distance) and potential energy
As the r increases, the potential energy also increases
Measurement of gravitational potential energy
J/kg
Describe the situation when an object in space falls into earths gravitational field
It starts with a potential energy relative to the earth of 0 and kinetic energy of 0. Then as it falls, the potential energy decreases(more negative) and the kinetic energy increases.
As long as the object is in orbit, _________.
There must be a gravitational force on it(centripetal force to keep it in orbit), so an object in orbit is not weightless
Astronauts in a space shuttle feel weightless because _______
They are in free fall
Orbital radius
The radius of the central body plus the height of the surface
Equations derived are for circular orbits but most objects are in _______
Elliptical orbits. (A circle is an ellipse with an eccentricity of 0)
Geosynchronous
When the satellite relative to the person moves at the same speed in which the earth rotates
If a satellite speeds up, ________
It will either move into a lower orbit or move into an elliptical orbit with the central body as one focus
As orbital radius decreases, _________.
Linear speed and angular speed increase so the angular momentum is constant