chapter 4 Flashcards
what type of quantity are forces
they are vectors, they have a push and a pull
what is newtons first law
it states that an object at rest with no forces acting on it will stay at rest
and an object at in motion with no forces acting on it will continue to move with constant velocity in a straight line
if you have no forces acting on an object, what is not present?
there would be no acceleration present
what is the only way to change a velocity
with a force
what is the agent in forces?
it is what enacts the push/pull motion
what are the two types of forces
contact forces and long-range forces
what are contact forces
they are forces that act on an object by touching it at a point of contact
what are long range forces
they are forces that act on an object without physical contact
(ex: gravity)
a swinger hits a baseball with a bat. What is the agent on the ball?
the bat is the agent as it is in direct contact with the object
what can you do if you have multiple forces present
you can combine all of the forces to form a net force and the motion will behave the same
what are the characteristics of a weight force?
weight forces are from the gravitational pull towards the center of the earth
it always points down, no matter the motion
the agent is the entire earth
what are the characteristics of a spring force?
have a push or a pull
a condensed spring will have a push force on an object (opposite direction)
a stretched spring will have a pull force on an object (the force is in the opposite direction of the displacement)
what are the characteristics of a tension force?
caused by a rope, chord, or string
can only exert a pulling force
the direction of the tension force is always the same as the direction the rope is pulled
what is a normal force
a normal force is a force that is exerted by the surface (the agent) against on object that is pushing against that surface
what direction is normal force?
it is always perpendicular to the surface the object is on
what direction is the normal force on a hand pushing on a wall?
it is horizontal and perpendicular, it is pushing against the hand
what direction is friction force generally?
it is always parallel to the surface
what are the two types of friction
static and kinetic
what is kinetic friction? when is it present
kinetic friction is the friction force caused by two surfaces sliding against eachother
it always opposes the direction of motion
it is indicated by noise being made and heat being generated
what is static friction
it is the friction that keeps an object stuck to a surface
it points in the direction necessary to prevent any motion
when we push a box to the right and it doesn’t move, what force is present and what direction is it?
static friction is keeping the box in place, it is directed to the left
when we push a box to the right hard enough and it starts to slide, what force is present? what direction is it?
kinetic friction, it still opposes us so it points in the left direction even though it is moving
when are normal forces present?
whenever we have an object in contact with a surface
when are friction forces present?
whenever we have a rough (not smooth) surface
when a car is rolling, what frictuon forces are exerted?
static friction on the wheels,
when we slam on the breaks, what force is present?
kinetic friction, it is loud and generates heat
what is drag force
it is the force present when an object is affected by a fluid resistance (water or air)
it points in the direction opposite of the motion
what is thrust
it is a force that pushes in the direction opposite of the motion, it propels the object forward by throwing something backwards
a constant force means what?
a constant acceleration
how can we use forces to connect to kinematics
the forces tell us the acceleration which can be used to solve for kinematics equations
how is acceleration related to force?
it is directly proportional
2x the force = 2x the acceleration
how is acceleration related to mass?
it is inversely proportional
2x the mass = 1/2 the acceleration
what is inertia?
it is a measure of how difficult it is to change the current acceleration of an object (related to mass)
what is newton’s third law
every force is a member of an action/reaction force pair that exerts an equal and opposite force (of the same kind) on eachother
what directions do the action and reaction forces point?
opposite of one another
if the force of object A pushes on B to the right
then the force of object B pushes on A to the left
if a action/reaction pairs exert equal and opposite forces on one another, how do we know which one will win and cause the other to move?
the one with more mass (it is less likely to change)
