Physics 2710 Exam III
December 10, 2012
Name:
Please circle the letter corresponding to the best answer.
1. At room temperature the product k BT is closest to
(a) 6x106 eV
(b) 1/40 eV
(c) 1 eV
(d) 12,000 eV
Questions 2-3 refer to: A macroscopic system con
Lecture 15
Collisions (1D, 2D; Elastic, Inelastic)
1
When there are no external forces present the momentum of a system will remain unchanged. (pi = pf)
If the kinetic energy before and after an interaction is the same, the "collision" is said to be elast
Lecture 14
Momentum Impulse Conservation of momentum Center of mass Motion of the center of mass
1
Consider two interacting bodies:
F21
F12
Fnet t If we know the net force on each body then v = at = m
The velocity change for each mass will be different if
Lecture 13
Relationship between conservative forces and PE Energy diagrams
1
How are conservative forces related to potential energy?
dW = F dr = -dU dU = -F dr
In 1-D:
W = F dr
dU ( x ) Fx = - dx F=- U
2
In 3-D:
The elastic potential energy of a spring:
Lecture 12
Potential energy Conservative forces Mechanical energy Conservation of energy Appendix: Conservative forces
1
Potential energy is energy associated with the configuration of a system of objects that exert forces on one another.
Gravitational po
Lecture 11
Springs Hooke's law Work by nonconstant forces Power
1
Springs
If I pull the spring to the right, the spring pulls to the left on me.
Experiments with some springs show that Fapplied spring stretch so that F = kx (Hooke's law).
2
The work done
Revision Exercises
Revision Exercises
The material on these slides has been collected from student papers over several years. I have removed source information for the sake of clarity. Look for what is wrong with each snippet. Problems may be grammar-rel
Lecture 23
Simple harmonic motion Mass and spring system
1
Simple harmonic motion (SHM) occurs when the restoring force (the force directed toward a stable equilibrium point) is proportional to the displacement from equilibrium.
2
The motion of a mass on
Lecture 22
Kepler's three laws Application: Detection of exoplanets
1
Johannes Kepler used observations made by Tycho Brahe to "discover" three laws of planetary motion.
http:/en.wikipedia.org/wiki/Johannes_Kepler
2
Kepler's 1st Law: The orbits of the pla
Lecture 21
Gravity Weight Gravitational field strength Work by gravity/gravitational potential energy Escape velocity
1
Gravity is the force between two masses. Gravity is a longrange or field force. No contact is needed between the bodies. The force of g
Lecture 20
Statics
1
The conditions for equilibrium are
F = 0 = 0
To have static equilibrium p = 0 and L = 0 too.
2
Center of gravity
If g is the same for all points within a body, then rcm = rcg.
An object that is 30 km tall will have a 1% variation in g
Lecture 19
Angular Momentum Conservation of angular momentum
1
Angular momentum
L = rp
The magnitude of L is
L = r p = rp
The direction of L is given by the right hand rule and its unit is kg m2/s.
2
Curl the fingers of your right hand so that they curl i
Lecture 18
Rolling Objects
1
Rolling An object that is rolling combines translational motion (its center of mass moves) and rotational motion (points in the body rotate around the center of mass). For a rolling object
K tot = K T + K rot 1 2 1 2 = mvcm +
Lecture 17
Torque Rotational form of Newton's 2nd law
1
A body can be set in rotational motion by the action of a torque. A rotating (spinning) body will continue to rotate unless it is acted upon by a torque.
hinge Q: Where on a door do you push to open
Lecture 16
and as vectors Rotational kinetic energy Moment of inertia Parallel axis theorem
It will be a good idea to review lecture 9.
1
Linear and angular motion
Independent Time-t variable Variable coordinate First derivative Second derivative Constan
Lecture 10
Work and Energy The scalar product Kinetic energy The work-energy theorem
1
Energy is a scalar quantity that is associated with a state (or condition) of an object.
Kinetic energy is associated with an object's state of motion. Potential energy
Lecture 9
Example of 2D motion: Circular motion Conditions for circular motion Examples
1
Circular Motion
y
f i
x
is the angular position. Angular displacement:
= f - i
Note: angles measured CW are negative and angles measured CCW are positive. is measu
Lecture 8
Examples using N2L
1
Example: A box slides across a rough surface. If the coefficient of kinetic friction is 0.3, what is the acceleration of the box?
y
FBD for box: fk;sb
Nsb
Apply Newton's 2nd Law:
F = N
x
sb
+ f k;sb + w eb = ma
web
F F
x y
=
Lecture 7
Mass vs. weight Examples of forces Gravity (long-range force) Normal force (contact force) Tension (contact force) Friction (contact force) Drawing free body diagrams
1
Mass vs. weight
Mass is an inherent property of a body, independent of the b
Lecture 6
Introduction to forces Newton's three laws Equilibrium
1
Isaac Newton was the first to discover that the laws that govern motions on the Earth also applied to celestial bodies.
Over the next few chapters we will study how bodies interact with on
Lecture 5
Motion in two and three dimensions Example of 2D motion: Projectile motion
1
A particle moves along the blue path as shown. At time t1 its position is r0 and at time t2 its position is rf.
y
v0 r vf
The instantaneous velocity points tangent to t
Lecture 4
Motion with constant acceleration Free Fall
1
Motion With Constant Acceleration
Consider an object with an acceleration a. What is the object's velocity as a function of time?
dv a= dt
This is a differential equation. Its solution is the functio
Lecture 3
Time and position Distance and displacement Velocity and speed Acceleration
1
Time
t1 would represent an instant of time as read from a clock.
The difference between two instants of time is a time interval: t = t2 t1.
2
Position, distance, and d
Lecture 2
Vector vs. Scalar Vector addition Unit vectors
1
Vectors versus scalars:
A vector is a quantity that has both a magnitude and a direction. A force is an example of a vector quantity. Vector magnitudes have units.
A scalar is just a number usuall
Lecture 1
Why study Physics? Physics Speak Units Approximations
1
Why Study Physics?
Physics is the foundation of every science (astronomy, biology, chemistry.) Many pieces of technology and/or medical equipment and procedures are developed with the help