The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 10
Due Wednesday, November 18, 2015, beginning of lecture. Write your answers neatly
and show the work necessary to follow your arguments.
1. A solid uniform cylinder of radius r, mass m and moment of inertia mr2 about its
sy
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 9
Due Wednesday, November 11, 2015, beginning of lecture. Write your answers neatly
and show the work necessary to follow your arguments.
1 (2 points) A hole is bored through a diameter of the earth. Assuming that the density
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 7
Due Friday, October 28, 2015, beginning of lecture. Write your answers neatly and show
the work necessary to follow your arguments.
1 (a) (2 points) A rod of length 2L and mass M lies on a frictionless table. A small ball o
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 4
Due Wednesday, September 30, 2015, beginning of lecture. Write your answers neatly
and show the work necessary to follow your arguments.
1. (2 points) A ring of mass M hangs from a thread. Two beads, each of mass m, slide o
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 8
Due Wednesday, November 4, 2015, beginning of lecture. Write your answers neatly and
show the work necessary to follow your arguments.
1 (2 points) We know how to calculate the maximum height reached by a particle if it is
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 3
Due Wednesday, September 23, 2015, beginning of lecture. Write your answers neatly
and show the work necessary to follow your arguments.
1. (1 point) A small rock moves in water. The magnitude of the resistive force exerted
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 6
Due Wednesday, October 14, 2015, beginning of lecture. Write your answers neatly and
show the work necessary to follow your arguments.
1. (2 point) Drum A is suspended by a massless string from drum B that rotates without
f
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 12
Due monday, November 30, 2015 (note special date), beginning of lecture. Write your
answers neatly and show the work necessary to follow your arguments
1. (2 points) In determining = Cp/Cv, the usual way is to measure the
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Phy1312 (Fall 2015): Homework 11
Due Wednesday, November 25, 2015, beginning of lecture. Write your answers neatly
and show the work necessary to follow your arguments.
1. (2 points) Doppler shift can be used to measure the speed of cars, to determine if
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Why cant a physical quantity have dimension log10(L)?
(for your interest only, not required for exams)
Recall that if a physical quantity A has dimension L2,
[A] = (L) = L2
a1 is the numerical value of A when mm is used as the unit of length (l1 = mm)
a2
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
POTENTIAL ENERGY & ENERGY
CONSERVATION
PHYS1312
Lecture 6
1
Intended Learning Outcomes
After this lecture you will learn:
1) gravitational and elastic forces as examples of
conservative force
2) properties of the potential energy function of a
conservati
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
GRAVITATION II
PHYS1312
Lecture14
1
Intended Learning Outcomes
! After this lecture you will learn:
1) Keplers laws of planetary motion
2) gravitation effect of a spherical mass distribution is the
same as a point mass
3) the apparent weight due to rotati
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
WAVE MOTION AND SOUND III
PHYS1312
Lecture 19
1
Intended Learning Outcomes
After this lecture you will learn:
1) Beats
2) The Doppler effect
3) Sound wave
2
Superposition of Sinusoidal Waves Case 3
(
12)
Assume two waves are
traveling in the same
direct
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
A.Temperature
B. Pressure
1
A19.1
A system can be taken from state a to state
b along any of the three paths shown in the
pV diagram.
If state b has greater internal energy than
state a, along which path is the absolute
value Q of the heat transfer the
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
THERMAL PROPERTIES OF
MATTER II
PHYS1312
Lecture 22
1
Intended Learning Outcomes
After this lecture you will learn:
1) heat capacity of gases, experimental and
theoretical aspects
2) distribution function as a statistical tool to
describe the microscopic
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
PRS
vacuum
What is Q and S when the partition is broken and the
ideal gas volume changes from V to 2V? Assume the walls
of the container are perfectly insulating.
A. Q = 0, S = 0
B. Q = 0, S > 0
C. Q > 0, S > 0
D. Q > 0, S < 0
11
A20.8
You put an ice cube
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
Entropy
PHYS1312
Lecture 25
1
Intended Learning Outcomes
After this lecture you will learn:
1) the relation between Entropy and disorder in a
system
2) Entropy in reversible processes, cyclic processes
and irreversible processes
3) Stating the second law
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
The vectors from the originvto 3 points
v v
A, B and C are a , b and c . Show that
the distance from the origin to the
plane ABC is
(
)
v v v
a b c
v v v v v v
a b + b c + c a
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
2D elastic collisions of two equal
masses
Will the cue ball go into the top right
pocket?
Momentum conservation
v
v
v
mv A1 = mv A2 + mvB 2
Assumptions: elastic collision, ignore
rotation of the balls
1
1
1 2
2
2
m v A1 = m v A 2 + mvB 2
2
2
2
Picture fro
The Hong Kong University of Science and Technology
PHYS 1312

Fall 2014
SECOND LAW OF
THERMODYNAMICS
PHYS1312
Lecture 24
1
Intended Learning Outcomes
After this lecture you will learn:
1) stating the second law of thermodynamics in
terms of heat engine and refrigerator
2) Carnot cycle as the most efficient heat engine
2
Heat
The Hong Kong University of Science and Technology
Calculus I
PHYS 1312

Fall 2016
PHYS1312 (Fall 2016) HW13 suggested solution
Problem 1
Since entropy is a state function, which depends on the starting and end points only, so we can
find the entropy change for the unknown processes by constructing a reversible process with the
same sta
The Hong Kong University of Science and Technology
Calculus I
PHYS 1312

Fall 2016
PHYS1312 (2016 Fall) HW3 Suggested Solution
Problem 1
In this problem, we define the right as positive. As there is no slipping between the boxes, the
acceleration for the boxes is the same, which is denoted as a.
Part i: F acting on M1
Consider the free
The Hong Kong University of Science and Technology
Calculus I
PHYS 1312

Fall 2016
PHYS1312 (2016 Fall) HW2 Suggested Solution
Problem 1
We set up an inertial reference frame outside the lift as shown in in Fig. 1. The position of the
pulley measured in this reference frame is denoted as (xp , yp ). Similarly, the position of box A
and
The Hong Kong University of Science and Technology
Calculus I
PHYS 1312

Fall 2016
PHYS1312 (Fall 2016) HW9 suggested solution
Problem 1
We denote the mass of the particle and the Earth as m and M respectively. The radius of the
Earth and the distance of the particle from the center are denoted as R and r respectively, with
r being posi