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

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
Odd Problems
Problem 43,
DEVELOPThetripcanbedividedintotwotimeintervals, and with
The
t2
t t1 t2 40 min (2 h/3).
totaldistancetraveledisx
25mi,where and t1 arethedistancescoveredineachtimeinterval.
x1 x2
x1
x2
EVALUATEDuringthefirsttimeinterval,
15min(or
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
1524
INTERPRET This problem is about hydrostatic equilibrium. Given the maximum pressure the submarine can
withstand, we want to find its maximum allowable depth below water.
DEVELOP The external pressure, p, at a depth, h, below the surface of water (wh
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
14.
If it were a reversible engine, its efficiency would be that of a Carnot engine, given by Equation 19.3:
eCarnot = 1
Tc
Th
Substituting the values given in the problem, we obtain
eCarnot =
1
Tc
2.7 K
=
1
=
1 4.82 104 99.95%
Th
5600 K
The engine effic
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
50.
(a) The rotational inertia of each of the rods perpendicular to the axis is 121 mL2 , and that of each rod parallel to the axis
is m( 12 L) 2 14 mL2. The total is I a [2( 121 ) 2( 14 )]mL2 23 mL2.
(b) The rotational inertia of a uniform thin rod, abou
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
10.
Coefficient of friction and Normal force are constant anywhere, Frictional force is also constant.
F = mg
Hence work done along path 1 is (FL) + (FL) = 2FL
Work done along path 2 is F *2L = 2FL
Conclusion : Force is not conservative.
30.
INTERPRET I
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
PH 141 General Physics 1 recommended problems  Chap.10
1.
A merrygoround starts from rest and accelerates with angular acceleration 0.01 rad/s
for 14 s. (a) How many revolutions does it make during this time? (b) Whats its average
angular speed?
Sol) T
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Ch.19 ()
41
45
49
53
59
A
D
B
C
41. The cycle consists of four paths; two are isochoric (constant volume) and the others are isobaric (constant
pressure).
Label the states in Fig. 19.22 A, B, C, D going clockwise from the upper left corner. The work done
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Odd number solutions for chapter 6
6.45
The rope tension can be decomposed by horizontal and vertical components. The work is done
by the horizontal component.
W = (T cos ) x = 2500J = (120N )(23m) cos
A calculator will give = 25.1 degree.
6.55
Kinetic e
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
19.
Tension kN
Weight kN
Since the pivot point is on the wall supporting the log, the normal force from it
does not affect the total torque. From here, we can find the difference of the
distance between the two points, one of which is center of gravity wh
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
Chapter 18. Heat, Work and the first law of Thermodynamics.
35. INTERPRET The thermodynamic process here is adiabatic, with no heat flowing between the system (the gas)
and its environment.
W . The
DEVELOP In an adiabatic process, Q = 0, and the first law
Korea Advanced Institute of Science and Technology
PHYSICS 101

Winter 2002
ch16 solution
February 27, 2015
18. we know absolute temperature T .
So, if we use equation 16.1 from text book,
TC = T 273.15
TC = 195.85 C
Also, we can get Fahrenheit degree by eqation 16.2.
TF =
9
TC + 32
5
Tc = 195.85 F
22. from equation 16.3,
Q = m
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