Transcript physicsELMS

By:
Morgan Henkelman
Elma Sakian
Lauren Cotter
Stephanie Wood
In “linear” motion, the whole object moves at
a uniform speed and distance. (In other
words, they all go to the same place, within
the same amount of time) However, in a
circular motion, two points on the same
object can be moving at different speeds and
different distances.
Rotational motion measures how long it takes a
point on an object to make a revolution. We
describe rotational motion using equations that are
very similar to those used in linear motion. The
main difference is that they are now accompanied
with the word, “angular.” Example: acceleration
becomes angular acceleration, etc.
Angular Velocity of an object:
w = ΔΘ÷ΔΤ
Angular Acceleration of an object:
a = Δ w÷ΔΤ
Torque: T=Fr sin Θ
Newton’s Second Law:
a=Tnet ÷I
Moment of Inertia of a point mass: I=mr
²
A 900 kg car makes a 180
degree turn with a speed of
10.0 m/s. The radius of the
circle through which the car is
turning is 25 meters.
Determine the force of friction,
and the coefficient of friction
acting upon the car.
The mass of the object can
be used to determine the
force of gravity acting in
the downward direction.
Use the equation
Fgrav = m * g
where g can be
approximated as 10 m/s/s.
Knowing that there is no
vertical acceleration of the
car, it can be concluded
that the vertical forces
balance each other. Thus,
Fgrav = Fnorm= 9000 N.
This allows us to determine
two of the three forces
identified in the free-body
diagram. Only the friction
force remains unknown
Known
Information:
m = 900 kg
v = 10.0 m/s
R = 25.0 m
Requested
Information:F
frict = ???
mu = ????
("mu" coefficient of
friction)
Since the force of friction is the only horizontal force,
it must be equal to the net force acting upon the
object. So if the net force can be determined, then the
friction force is known. To determine the net force,
the mass and the kinematic information (speed and
radius) must be substituted into the following
equation:
Substituting the given values yields a net force of
3600 Newtons. Thus, the force of friction is 3600 N.
Finally the coefficient of friction ("mu") can be
determined using the equation which relates the
coefficient of friction to the force of friction and the
normal force.
Substituting 3600 N for Ffrict and 9000 N for Fnorm
yields a coefficient of friction of 0.400.
Amusement park rides that spin are
designed to thrill riders using the physics
of rotational motion. The thrill is produced
by a “force” that is present only when the
ride spins.