Advanced Physics Chapter 5 Circular Motion: Gravitation.
-
Upload
anna-francis -
Category
Documents
-
view
225 -
download
1
Transcript of Advanced Physics Chapter 5 Circular Motion: Gravitation.
Advanced Physics
Chapter 5Circular Motion: Gravitation
Chapter 5: Circular Motion: Gravitation
5-1 Kinematics of Uniform Circular Motion5-2 Dynamics of Uniform Circular Motion5-3 Highway Curves, Banked and Unbanked5-4 Nonuniform Circular Motion5-6 Newton’s Law of Universal Gravitation5-7 Gravity near the Earth's Surface5-8 Satellites and “Weightlessness”5-10 Types of Forces in Nature
5-1 Kinematics of Uniform Circular Motion
Uniform Circular Motion
object that moves in a circle with constant speed
magnitude of velocity is constant but direction is changing
5-1 Kinematics of Uniform Circular Motion
Centripetal (radial) acceleration (ar or ac)
center-seeking acceleration
acceleration directed toward the center of the circle
velocity and acceleration vectors are perpendicular to each other
5-1 Kinematics of Uniform Circular Motion
Velocity v = d/t d = 2rso v = 2r/Twhere T = period of
revolution (sec)and f = frequency
(sec-1)T = 1/f
5-1 Kinematics of Uniform Circular Motion
Centripetal acceleration
aR = v2/r
aR = 42r/T2
5-2 Dynamics of Uniform Circular Motion
According to Newton’sSecond Law: Fnet = ma
FR = maR = mv2/r
net centripetal force (FR) must be directed toward center (why?)
centripetal force vs. centrifugal force
5-3 Highway Curves, Banked and Unbanked
When a car goes around a curve in the road what keeps it on the road?
When is the friction between the tires and the road greater, when they are rolling or sliding?
So to keep a car on the road on a curve we must……
5-3 Highway Curves, Banked and Unbanked
Banking a curve reduces skidding why?
Fn is at an angle toward the center of the curve
so a portion of the Fn goes into FR so the tires need to supply less frictional force to make up for the remaining FR needed
5-3 Highway Curves, Banked and UnbankedBanking angle of roadFnsin = mv2/r
since Fncos = mg then Fn = mg/cos
mg(sin /cos) = mv2/r
g(tan ) = v2/rtan = v2/rg so banking angle of road
doesn’t depend on m, just v,r and g
5-4 Nonuniform Circular Motion
For an object in UCM; the only acceleration is due to radial (centripetal) acceleration
aR is caused by what? Equation?But if the object in circular motion is
speeding up or slowing down there is another type of acceleration, tangential acceleration
5-4 Nonuniform Circular Motion
Tangential acceleration (atan)Acceleration caused by the
change in the magnitude of the velocity of an object moving in a circular path
atan = v/t
5-4 Nonuniform Circular Motion
Total vector acceleration (a)Acceleration caused by the change
in the magnitude and direction of the velocity of an object moving in a circular path
It is the sum of both the tangential and radial acceleration of an object
a = atan + aR
5-4 Nonuniform Circular Motion
Total vector acceleration (a)
a = atan + aR
The magnitude of a at any moment is:
a = (a2tan + a2
R)1/2
5-6 Newton’s Law of Universal Gravitation
Newton’s Law of Universal Gravitation
every particle in the Universe attracts every other particle with a force that is proportional to their masses and inversely proportional to the distance between them
5-6 Newton’s Law of Universal Gravitation
Newton’s Law of Universal Gravitation
the force of gravity acts along a line joining the two particles.
F = Gm1m2/d2
G = 6.67 x10 –11
Nm2/kg2
5-6 Newton’s Law of Universal Gravitation
Find the force of gravity between two electrons that are 2.3x10-2 nm apart
Answer: 1.05 x 10-49 N
5-7 Gravity near the Earth's Surface
Since the force of gravity is equal to the weight of an object…
Gmome/r2 = mogso….g = Gme/r2
so..gravity (g) doesn’t depend on the mass of the object, just G, me and r!
5-8 Satellites and “Weightlessness”
Why do satellites orbit the Earth?
How can a person orbiting the Earth experience “weightlessness”?
Many nasty effects of weightlessness on the body
5-8 Satellites and “Weightlessness”
What is the relationship between Fn, Fa, and Fg in the following situations?
stationaryaccelerating upaccelerating down in free-fall
5-10 Types of Forces in Nature
Four different fundamental forces:
gravitational force force between any two objects
electromagnet force force between any two charged
objects
strong nuclear force force that holds the nucleus together
weak nuclear force force involved in certain types of
nuclear decay
5-10 Types of Forces in Nature
What is GUT?