gravity
aforce of attraction between objects due to their masses
law of universal gravitation
newton's law describes the relationships between gravitational force, mass and distance. it is thought to apply to all objects in the universe. "all objects attract each other thru gravitational force. the magnitude of the force depends on the masses of t
how does mass affect gravitational force?
gravitational force is small between small-massed objects but larger between greater-massed objects
how does distance affect gravitational force?
gravitational force=large between 2 objects that have a small distance between them. small when a big distance
weight
measure of gravitational force on an object. can differ on different planets. planets that are larger have more gravitational force, so you weigh more. vice versa.
mass
a measure of the amount of matter in an object. doesn't differ when gravitational force changes
how does gravity act on moving and nonmoving objects?
it can cause objects to move. it pulls static objects downward, but they don't move downward because the force is BALANCED by an upward force.
terminal velocity
when the air resistance on a falling object is equal to the gravity acting on it. the net force is 0N and the object is a a constant velocity
free fall
when a falling object is only being pulled down by gravity and no other forces are acting on it
projectile motion
the curved path an object follows when thrown or propelled near Earth. 2 types of motion are horizontal movement and vertical. why you have to aim above a target
horizontal movement (projectile)
your hand applies a force to throw the ball (this force gives it the horizontal motion). after the ball leaves your hand, no horizontal forces or gravity are acting on it, so there are no forces to change the ball's velocity, so it's constant after it lea
vertical movement
gravity pulls everything to the center of the Earth. after the ball is thrown, it is pulled down at an accel. of 9.8 m/s2
orbiting
an object moves around another in space. the object is in freefall toward what it's orbiting, but also moves forward. these movements combined make an orbit.
centripital force and orbiting
orbiting objects always change direction so there is an unbalanced force on them. this force is centripital force, making them move in ellipses. this force is provided by gravity.
air resistance
the force that opposes th motion of objects through air. magnitude depends on size, shape and speed of an object.
why do objects fall to earth at the same rate?
accel. due to gravity is the same for all objects near Earths surface (9.8 m/s2). accel. depends on force and mass.
how does accel. depend on force and mass?
a heavy object has more gravitational force then a lighter one, but is harder to accelarate because it has more mass. vice versa for a light one. the differences make up for eachother and the accel. is the same.
equation for accel.
a=vf-vi
t
inertia
the tendency of an object to resist being moved or, if the object is moving, to resist a change in speed or direction until an outside force acts on the object. mass is a measure of inertia
why is a small-massed object easier to change the motion of?
it has less inertia than a larger-massed object
newton's 1st law of motion
an object at rest stays at rest and an object in motion remains in motion at a constant velocity in a straight line unless acted on by an unbalenced force
why do things stop after pushed?
the unbalenced force of friction changes the motion of an object. without it, objects pushed would go on forever at a constant velocity
newton's second law of motion
the accelaration of an object depends on the mass of the object and the amount of force applied to it. (big mass, it takes more force to accelarate it. vice versa for little) (more force, more accelaration)
in what direction is accelaration?
in the same direction of the net force applied
newton's 3rd law
whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first (all forces act in pairs)