38 terms

# Force Unit Test

#### Terms in this set (...)

What is Newton's first law?
Inertia
Inertia
(1st Law) the resistance an object has to change in its state of motion
-if the forces acting on an object are balanced, the acceleration of the object is 0 m/s/s
-predicts the behavior of objects where all existing forces are balanced
-the more mass an object has the more inertia it has
mass
A measure of the amount of matter in an object - solely dependent on the inertia of an object.
weight
an object's mass times the force of gravity; the force of gravity on Earth is always equal to the weight of the object as calculated: weight = m x g
state of motion
motion of an object is defined by its velocity- the speed with a direction
mechanical equilibrium
(ΣF)- when all the forces that act upon an object are balanced; net force is 0 and the acceleration is 0m/s
objects in equilibrium are either:
*in static equilibrium- at rest and staying at rest
*in dynamic equilibrium- in motion with constant velocity
force
a push or pull; a vector quantity (magnitude & direction)
Newton
the metric unit for force; is the amount of force required to give 1kg of mass an acceleration of 1 m/s2 1 Newton = 1 kg x m/s2
Balance force
equal forces acting on one object in opposite directions; will not change the object's motion (net force of zero), each force balances the other.
Unbalanced force
a net force that can cause an object to start moving, stop moving, or change direction;
an unbalanced force acting on an object will change the object's motion or state of motion
Net force
the combination of all forces acting on an object; determines whether an object moves & in which direction it moves
Types of contact forces
frictional
tensional
normal
air resistance
applied
spring
Frictional Forces (Ffrict)
the force exerted by a surface as an object moves across it or makes an effort to move across it
Tensional Forces (Ftens)
The force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends; tension force is directed along the length of the wire & pulls equally on the objects on the opposite ends of the wire
Normal Forces (Fnorm)
the support force exerted upon an object that is in contact with another stable object;
example: if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book
Air Resistance Forces (Fair) (drag)
a special type of frictional force that acts upon objects as they travel through the air; is often observed to oppose the motion of an object; is most noticeable for objects that travel at high speeds or objects with larger surface area
Applied forces (Fapp)
a force applied to an object by a person or another object; if a person is pushing a desk across the room, then there is an applied force acting upon the object
Spring Force (Fspring)
the force exerted by a compressed or stretched spring upon any object that is attached to it; an object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position; for most springs the magnitude of the force is directly proportional to the amount of stretch or compression of the spring
Types of Distance Forces
Gravitational Pull
Electric Forces
Magnetic Forces
Gravitational Pull
the unbalanced force that pulls objects toward each other; on Earth, gravity is a downward force
Electric Forces
the attraction or repulsion between electric charges
Magnetic Forces
the attraction or repulsion between magnetic poles
Field
a region of influence used to understand forces that act at a distance
Strength of friction is determined by:
* the types of surfaces involved
* how hard the surfaces push together
Types of Frictional Forces
Static Friction
Kinetic Friction (sliding friction)
Rolling Friction
Fluid Friction
Static Friction
friction that acts on objects not moving
Kinetic Friction (sliding friction)
friction arising between bodies in motion with respect to each other occurs when two solid surfaces slide over each other
Rolling Friction
When an object rolls across a surface; is easier to overcome than sliding friction for similar materials; engineers design ball bearings reduce the friction between two moving surfaces
Fluid Friction
occurs when a solid object moves through a fluid; types of fluids are water, oil & air
Newton's 2nd Law of Motion formula
F net = m x a OR a = F net/m
Newton's 2nd Law of Motion
pertains to the behavior of objects for which all existing forces are not balanced
The acceleration of an object is dependent upon two variables:
* the net force (F net) acting upon the object
* the mass of the object
The proportional relationship between F net & acceleration
when mass stays the same, acceleration & F net are directly proportional;
example: as F net increases, the acceleration also increases
The proportional relationship between mass & acceleration
when F net stays the same, acceleration & mass are inversely proportional;
example: as mass increases, the acceleration decreases
A common misconception regarding Newton's 2nd Law
Sustaining motion requires a continued force;
Remember: forces do not cause motion; forces cause accelerations
Action/Reaction (3rd Law of Motion)
Forces always come in pairs - equal & opposite action-reaction force pairs
In every interaction, there is a pair of forces acting on the two interacting objects
* the size of the forces on the first object equals the size of the force on the second object
* the direction of the force on the first object is opposite to the direction of the force on the second object