Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
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Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
11. According to the Archimedes Principle, the objects stop rising when their
mass become equal to the weight of the original fluid volume. In other words,
objects
density
and
original
fluid
density
become
same.
In
the
case
of
heliumfilled balloon, densi
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
26
The wave speed corresspond to root(gh). See eq 14.5
34
Lets suppose speed of light is infinity. Time delay is 100m/ (334m/s). Almost 0.3s
44
By eq 14.15, new f is f / (1 (17/343)=380/0.95=400
48
Amplitude is 3cm, wavelength is 8cm, T is 10.4s, and spe
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Chapter 9 odd number solutions
41.
Since the cone has constant density, we know by inspection that the centre of mass is along the
axis of the cone. We need to find out how high the centre of mass is along the axis i.e.
.
The volume of each mass elements
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
16.(a) The change in the internal energy of the water is U mcT , and the work done by it (i.e., the
negative of the work done on it) is given. Therefore, Equation 18.1 gives
Q U W (0.5 kg)(4.184 kJ/kg K)(3 K) (9.0 kJ) 6.28 kJ 9.0 kJ 2.72 kJ. (The
negative
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
11.
In this problem we want to find the work done by the frictional force in moving a block from
one point to another over two different paths.
Figure 7.16 is a plan view of the horizontal surface over which the block is moved, showing
the
paths (a) and (
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 10 Rotation
101 Rotational Variables
Circular motion vs. rotational motion
Angular velocity
=
d
dt
(rad/s),
angular acceleration
=
d d 2
=
dt d t 2
(rad/
2
s )
102 Rotation with Constant Angular Acceleration
= 0
0= 0 t
Rotation with constan
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 17 WavesII
*Chapter 16 gave a general theoretical treatment of a wave that can be applied to any
wave. Here in Chapter 17 we deal specifically with the sound wave. The sound wave
belongs to a longitudinal wave, that is, the vibrational motion of
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 37 Relativity
* Two mainstreams of modern physics are quantum physics and relativity. Quantum
physics, developed by Planck, Einstein, Bohr and many others, deals with the microscopic
world. Relativity, developed singlehandedly by Einstein, deals
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 13 Gravitation
*Newton discovered his law of (universal) gravitation that two masses attract each
other, by observing an apple falling to the ground and the Moon circling around the
Earth. In this chapter, we study motion of the Moon and satellite
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 12 Equilibrium and Elasticity
*So far, we have considered objects in motion. In this chapter, we consider forces
acting on stationary objects. One may wonder if there is anything interesting to talk
about forces on stationary objects, but these ar
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 9 Center of Mass and Linear Momentum
91 The Center of Mass
The center of mass of a system of particles is the point that moves as though (1)
all of the systems mass were concentrated there and (2) all external forces were
applied there.
n
mi r i
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 8 Potential Energy and Conservation of Energy
* There are two types of force, conservative and nonconservative. When the force is
conservative, the amount of work done by that force is independent of the path and
depends only on the end points. Or
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 7 Kinetic Energy and Work
* In Chapters 7, 8 and 9, we study two important quantities, energy and momentum.
Energy and momentum provide another way of describing motion, often a very useful
way due to the conservation laws of energy and momentum.
Korea Advanced Institute of Science and Technology
PHYSICS 101

Fall 2014
Chapter 15 Oscillations
*There are three types of motion: translational, rotational and oscillatory(vibrational).
We have already met the first two types. Now is the time to study the last one, namely
oscillatory motion.*
151 Simple Harmonic Motion
*The
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
40.
With the carbon atom end of either spring fixed, the frequency of either oxygen atom is=
2=
f
Therefore k= (2 4 1013 Hz) 2 (16 1.66 1027 kg)= 1.68 103 N/m.
50.
INTERPRET In this problem we want to find the radius of the solid disk such that its verti
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
26.
problem)
A 3.0mdiameter merrygoround with rotational inertia
is spinning freely at 0.50 rev/s.
Four 25kg children sit suddenly on the edge of the merrygoround. (a) Find the new angular
speed, and (b) determine the total energy lost to friction
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Ch.4 Solutions for Even number
16. Let the initial speed as v0. The final speed is obviously 0. We can examine the stopping force,
f=ma by using Eq. 2.11, v 2 =
v02 + 2a ( x x0 ). Using v=0, the stopping distance is given by (since a<0)
02
=  =
2 0 
Th
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
9. The intensity of light from a localized source decreases as the inverse
square of the distance from the source. Does this mean that
the light loses energy as it propagates?
ANS: No it doesnt, the change is density of energy, not total energy
29. A tran
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Solutions of Suggested Problems in Chap.3
PH141 TA : Kim On
23. (a) If one wants to know a pure speed of the tip of the hour hand,
one should measure the distance it moved rather than the position vector.
In that case, the tip of the hour hand travels the
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Suggested Problem Ch. 5 Newtons Law
20.
With reference to the solution to Exercise 19, the parallel component of the equations of motion for the
masses are TL mL g sin 60 =mL aL and mr g sin 20 Tr =mr ar . The accelerations and tensions are equal,
respect
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Sol]
1. [840] A white dwarf is a collapsed star with roughly the Suns mass compressed into the
size of Earth. What would be (a) the orbital speed and (b) the orbital period for a spaceship
in orbit just above the surface of a white dwarf?
(a) The radius
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Chapter 13 Solution
23.
The frequency of the automobile is,
f=
1 26/
1
=
= 0.589
2 2 1900
The Period of the automobile is,
T=
1
= 1.698
43.
(a) Right after the mass leaves the spring, the masss speed will be 0 . It means that
the mass is in contact wit
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Num 41.
Using Equation of Kepler,
T2 =
4 2 r3
GM
(1)
We can calculate mass of galaxy. T = 200M y = 200106 365243.6103 s,
and r = 2.6 1020 m, then M is following,
M=
4 2 r3
= 1.57 1057 kg.
GT 2
(2)
Num 43.
Gravitation force focusing on the center makes 3 b