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Chapter 4
Forces & Newton's Laws of Motion
46
Physics
Undergraduate 2
01/16/2015

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Term
force
Definition
a push or a pull
Term
contact forces
Definition
forces that arise from physical contact between two objects (ex. throwing a basketball or pulling a water skier)
Term
noncontact forces/action-at-a-distance forces
Definition
forces that objects exert on one another even though they are not touching
Term
Is mass a scalar or vector quantity?
Definition
scalar
Term
Newton's first law of motion
Definition
an object continues in a state of rest or in a state of motion at a constant velocity unless compelled to change that state by a net force
Term
net force
Definition
the vector sum of all forces acting simultaneously on a body
Term
What is the purpose served when a net force acts on an object?
Definition
to change the object's velocity, not to sustain it
Term
inertia
Definition
the natural tendency of an object to remain at rest or in motion at a constant velocity
Term
mass
Definition
a quantitative measure of inertia
Term
SI unit of inertia & mass
Definition
kilogram (kg)
Term
How are mass and inertia correlated?
Definition
the larger the mass, the greater the inertia
Term
Can "mass" and "weight" be used interchangeably?
Definition
no!
Term
Are accelerating reference frames inertial or noninertial?
Definition
noninertial
Term
inertial reference frames
Definition
one in which Newton's first law of inertia is valid
Term
Newton's second law of motion
Definition
when a net external force "sigma vector F" acts on an object of mass "m", the acceleration "vector a" that results is directly proportional to the net force & had a magnitude that is inversely proportional to the mass; the direction of the acceleration is the same as the direction of the net force; "vector a" = "sigma vector F"/"m"; "sigma vector F" = "m"("vector a")
Term
SI unit of force
Definition
kg(m)/s^2 (Newton) (N)
Term
external forces
Definition
forces that the environment exerts on the object of interest
Term
internal forces
Definition
forces that one part of an object exerts on another part of the object
Term
Is the newton a derived or base SI unit?
Definition
derived
Term
CGS unit for mass
Definition
gram (g)
Term
CGS unit of acceleration
Definition
centimeter/second^2
Term
CGS unit for force
Definition
dyne (dyn)
Term
BE unit for mass
Definition
slug (sl)
Term
BE unit for acceleration
Definition
foot/second^2
Term
BE unit for force
Definition
pound (lb)
Term
free-body diagram
Definition
a diagram that represents the object & the forces that act on it
Term
Only the forces that _____ appear in a free-body diagram
Definition
act on the object
Term
Newton's third law of motion/the "action-reaction" law
Definition
whenever one object exerts a force on a second object, the second object exerts an oppositely directed force of equal magnitude on the first object; for every action there is an equal, but opposite, reaction
Term
3 fundamental forces
Definition
1. gravitational force
2. strong nuclear force
3. electroweak force
Term
Newton's Law of Universal Gravitation
Definition
every particle in the universe exerts an attractive force on every other particle; F = G(m1m2/r^2)
Term
What does "G" (universal gravitational constant) equal in Newton's Law of Universal Gravitation?
Definition
6.674 x 10^-11 N m^2/kg^2
Term
What does "r" mean in Newton's Law of Universal Gravitation?
Definition
the distance between the center of masses of the objects/particles
Term
weight
Definition
the gravitational force that the earth exerts on an object
Term
SI unit for weight
Definition
newton (N)
Term
equation for weight
Definition
W = G(ME x m)/r^2 OR W = m(g)
Term
normal force (vector FN)
Definition
the component of the force that a surface exerts on an object with which it is in contact that is perpendicular to the surface
Term
When does FN = W?
Definition
if an object is resting on a horizontal surface & there are no vertically acting forces except the object's weight & the normal force
Term
Does the normal force always have the same magnitude of the weight of an object?
Definition
no!
Term
When does the apparent weight not equal the true weight?
Definition
if the scale and the person on it are accelerating
Term
apparent weight
Definition
the force that an object exerts on a scale with which it is in contact
Term
equation for apparent weight
Definition
FN = m(g) + m(a)
Term
frictional force (friction)
Definition
the component of the force that is parallel to the surface when the object moves or attempts to move along a surface
Term
maximum static frictional force (vector fsMAX)
Definition
the force just before breakaway
Term
equation for kinetic frictional force
Definition
fk = uk(FN)
Term
What is the main difference between static friction & kinetic friction?
Definition
static: opposes the impending relative motion between two objects
kinetic: opposes the relative sliding motion that actually does occur
Term
equilibrium
Definition
when an object has zero acceleration
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