Unit 2: Forces and Motion Flashcards
Applied Force (Fa)
a general term for the forces that move objects such as rockets, planes, cars, and people
-points in the same direction as the acceleration of the object, canceling out any resistive forces
Gravitational Force (Fg)
a field force due to the gravitational attraction between two objects, generally Earth and an object
-points straight down towards the center of the Earth
Friction Force (Ff)
The contact force that acts to oppose sliding motion between surfaces (can be static or kinetic)
- points parallel to the surface and usually opposite the direction of sliding
Normal Force (FN)
The contact force exerted by a surface on an object
-points perpendicular to and away from the surface
Tension Force (FT)
The pull exerted by a string, rope, or cable when attached to a body when pulled taut
-points away from the object and parallel to the string, rope, or cable at the point of attachment
Spring Force (Fsp)
a restoring force; that is, the push or pull a spring exerts on an object
-points opposite the displacement of the object at the end of the spring
Air Resistance (Ffk)
a special type of frictional force that acts upon objects as they travel through the air
-points opposite the displacement of the object at the end of the spring.
Newton’s First Law
An object at rest remains at rest and an object in motion continues in motion with constant velocity (constant speed in a straight line) unless the object experiences a net external.
Newton’s Second Law
The acceleration of an object is directionally proportional to the net external force acting on the object and inversely proportional to the object’s mass.
Newton’s Third Law
If two objects interact, the magnitude of the force exerted on object 1 by object 2 is equal to the magnitude of the force simultaneously exerted on object 2 by object 1. These two forces are opposite in direction.
always the same type of force but the on’s and by’s switch
ex:
Fn on B by A
Fn on A by B
Force
an interaction between two objects that results in a push or a pull
Forces can cause… (3 things)
- a stationary object to move
- a moving object to stop
- a moving object to change direction
2 Types of Forces
Contact Force
- Forces that result from physical contact between two objects
Field/Long Range Forces
- forces that do not involve physical contact between two objects
Kinetic Friction Force (Ffk)
a force that acts to slow down an object in motion
-sliding friction
-resistance force
Static Friction Force (Ffs)
a force that acts when an object is on the verge of motion
-prevents object from moving
not moving but it looks like is should move
Centripetal Net Force (FnetC)
the net (total) force directed towards the center of an object circular path
Centripetal Acceleration (ac)
acceleration directed towards the center of a circular path
Tangential Velocity
velocity at the line tangent to the circular path
Inertia
The tendency of an object to resist being moved, or if already moving, to resist a change in speed or direction
How do we measure inertia?
Mass: the amount of matter in an object, different from the weight
weight vs. mass
Mass is the amount of matter in the object and weight is the amount of gravitational pull an object has which can change on different planets.
The more mass something has… (inertia increases or decreases)
As mass increases inertia increases, meaning it will take more force to change it’s speed or direction
Free Body Diagram
force diagram used to analyze the forces affecting the motion of a single object
Force Diagram
a diagram that shows force factors as arrows
External Force
a single force that acts on an object as a result of the interaction between the objects and its environment
system
the object that is under consideration
surroundings
everything else in the environment that might significantly affect the system
Action force
The force that object 1 exerts an object 2
Reaction Force
the force that object 2 exerts on object 1
not exactly a reaction because it occurs simultaneously with the reaction force
weight (Fg)
a measure of the gravitational force exerted on an object
Field
a region in which an object experiences a force as a result of the presence of some other object
ex: things on earth experience gravitational force because of it’s presence
g=9.8
Earth’s Gravitational Field Strength
Newton (N)
The force required to give 1 kg of mass and acceleration of 1 m/s/s
(kgm/s^2)
2nd Law Equation:
Fnet = msystem(a)
or
a = Fnet / msystem
Assumptions about Friction
- the relationship between FN and Ff affects friction
- friction depends on the composition and qualities of the surface and contact with each other
Coefficient of Friction (μ)
The quantity that expresses the dependence of frictional forces on the particular surfaces in contact
(a number representing the interactions between surfaces)
