Physics (Midterms - Concepts) Flashcards
describes the relationship between the motion of objects in our everyday world and the forces acting on them
dynamics
Language of Dynamics
Force and Mass
the measure of interaction between two objects (pull or push). It is a vector quantity - it has a magnitude and direction
force
the measure of how difficult it is to change object’s velocity (sluggishness or inertia of the object)
mass
may be a contact force or field force
forces
it result from physical contact between two objects
contact forces
it act between disconnected objects and it is also called as “action at a distance”
field forces
Forces
gravitational force
archimedes force
friction force
tension force
spring force
normal force
a resultant force acting on object
net force
an object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force
newton’s first law
it is defined as the vector sum of all the external forces exerted on the object
net force
is a property of objects to resist changes in motion
inertia
is a measure of the amount of inertia
mass
is a measure of the resistance of an objects to changes in its velocity
mass
is an inherent property of an object
mass
the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass
newton’s second law
also measured in lbs, is a force (mass x acceleration)
weight
the magnitude of the gravitational force acting on an object of mass m near the earth’s surface is called the
weight
it can also be found from the law of universal gravitation
g
it has a unit of N
weight
force from a solid surface which keeps object from falling through
normal force
its direction is always perpendicular to the surface
normal force
it direction is pointing downward
gravitational force
a taut rope exerts forces on whatever holds its ends
tension force
its direction is always along the cord (rope, cable, string,…) and away from the object
tension force
if object 1 and object 2 interact, the force exerted by object 1 on object 2 is equal in magnitude but opposite in direction to the force exerted by object 2 on object 1
newton’s third law
either force can be the action or reaction force
newton’s third law
the most important step in solving problems involving Newton’s laws
free body diagram
objects that are either at rest or moving with constant velocity are said to be in equilirbium
objects in equilibrium
if an object that can be modeled as a particle experiences an acceleration, there must be a non-zero net force acting on it
accelerating objects
4 basic quantities in kinematics
displacement
velocity
time
acceleration
any motion involves three concepts
displacement
velocity
acceleration
it can be defined as the change of position over time
motion
is a change of position in time
displacement
it is a vector quantity. it has both magnitude and direction and it has units of length in meters
displacement
rate of change of position
velocity
it is a vector quantity. it has both magnitude and direction. it has a length/time in meter per second1
velocity
is the slope of the line segment between end points on a graph
average velocity
total distance over time interval
average speed
it means “at some given instant”
instantaneous
it indicated what is happening at every point of time
instantaneous velocity
is the special case of constant velocity
uniform velocity
it means “an acceleration is present”
changing velocity or non-uniform
rate of change of velocity
acceleration
is the slope f the line connecting the initial and final velocities on a velocity-time graph
average acceleration
object moving along a curved path with constant speed
circular motion
is one type of 2D motion under constant acceleration
projectile motion
is the study of the basic components of the universe and their interactions
physics
are used in many practical applications, including construction
principles of physics
it is very useful during the process of understanding phenomena
models
is detailed and can give testable predictions
theory
a brief description of how nature behaves in a broad set of circumtances
law
is similar to a law, but applies to a narrower range of phenomena
principle
is the internationally accepted system of units for measurement in all of the sciences, including physics
SI, or metric system of units
is defined as a ratio of units that is equal to 1
conversion factor
are the base units that make it up: they are generally written using square brackets
dimensions of a quantity
is the checking of dimensions of all quantities in an equation to ensure that those which are added, subtracted, or equated have the same dimensions
dimensional analysis
3 factors that determine the effectiveness of the force in opening the door:
the magnitude of the force
the position of the application of the force
the angle at which the force is applied
is the tendency of a force to rotate an object about some axis. it is a vector quantity
torque
it is also known as “Moments of a Force”
torque
is the perpendicular distance from the axis of rotation to a line drawn along the direction of the force
moment arm, d
are diagrams used to show the relative magnitude and direction of all forces acting upon an object in a given situation
free-body diagrams
types of forces
applied force
gravity force
normal force
friction force
air resistance force
tension force
is a force that is applied to an object by a person or another object
applied force
also known as weight, is the force with which the earth, moon, or other massively large object attracts another objects towards itself
gravity force
is the support force exerted upon an object that is in contact with another stable object
normal force
is the force exerted by a surface as an object moves across it or makes an effort to move across it
friction force
There are at least two types of friction force
sliding friction
static friction
is a special type of frictional force that acts upon objects as they travel through the air
air resistance force
is 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
This is the force system in which lines of action of individual forces lie in the same plane but act at different points of applications.
non-concurrent force system
Lines of action of individual forces are parallel to each other
parallel force system
Lines of action of the forces are not parallel to each other
non-parallel force system
is the tendency of a force to make a rigid body to rotate about an axis. This is a vector quantity having both magnitude and direction.
moment
rotational tendency
moment
This is the axis about which rotational tendency is determined. It is perpendicular to the plane comprising moment arm and line of action of the force
moment axis
This is the position of axis on co- planar system.
moment center
Perpendicular distance from the line of action of the force to moment center.
moment arm
it is computed as the product of the force and the perpendicular distance from the line of action to the point about which moment is computed
magnitude of moment
is a system of forces whose magnitude of the resultant is zero.
couple
is composed of two equal forces that are parallel to each other and acting in opposite direction.
couple
A couple is completely defined by following elements:
The magnitude of its moment
The plane in which it acts defined by the direction of the normal to the plane.
The direction of rotation in the plane that is the sense of the couple.
is a vector quantity having the direction normal to the plane in which it acts.
moment of a couple
The plane in which the two forces forming a couple lie
plane of the couple
the distance between their line of action
arm of the couple
types of loads on beams
Concentrated Loads
Uniformly distributed load
Uniformly varying load
This is the load acting for very small length of the beam.
Concentrated Loads
Also known as point load
Concentrated Loads
This is the load acting for a considerable length of the beam with same intensity of w kN/m throughout its spread.
Uniformly distributed load
This load acts for a considerable length of the beam with intensity varying linearly from ‘0’ at one end to w kN/m to the other representing a triangular distribution
Uniformly varying load
is the physical science concerned with the behavior of bodies that are acted upon by forces
Mechanics
is the study which deals with the condition of bodies in equilibrium subjected to external forces.
Statics
is also a branch of mechanics in which the forces and their effects on the bodies in motion are studied
Dynamics
Dynamics is sub-divided into two parts
Kinematics
Kinetics
deals with the geometry of motion of bodies without and application of external forces.
Kinematics
deals with the motion of bodies with the application of external forces.
Kinetic
It is defined as a definite amount of matter the parts of which are fixed in position relative to one another under the application of load.
Rigid Body
It is that agent which causes or tends to cause, changes or tends to change the state of rest or of motion of a mass.
force
A force is fully defined only when the following four characteristics are known:
Magnitude
Direction
Point of application
Sense
consists of forces that lie in the same plane.
coplanar force system
are commonly encountered in two-dimensional problems and are often analyzed using methods such as vector addition or graphical techniques like the method of polygons.
Coplanar force systems
the lines of action of the forces do not intersect at a single point
non-concurrent force system
all the forces have their lines of action intersecting at a single point.
concurrent force system
If two forces acting at a point are represented in magnitude and direction by the two adjacent sides of a parallelogram, then the resultant of these two forces is represented in magnitude and direction by the diagonal of the parallelogram passing through the same point.
Parallelogram law of forces
If two forces acting at a point can be represented both in magnitude and direction, by the two sides of a triangle taken in tip to tail order, the third side of the triangle represents both in magnitude and direction the resultant force F, the sense of the same is defined by its tail at the tail of the first force and its tip at the tip of the second force’.
Triangle law of forces
is the effect of a force in a certain direction. A force can be split into infinite number of components along infinite directions.
Component of a force
is any quantity in physics that has MAGNITUDE ONLY
scalar quantity
is any quantity in physics that has BOTH MAGNITUDE and DIRECTION
vector quantity
are represented by drawing arrows
vectors
Aligning vectors head to tail and then drawing the resultant from the tail of the first to the head of the last
graphical method
