Copy of HKISO FINAL ROUND Session 1 & 2 - S3 and SS.pdf

Session 1 & 2 - Secondary 3
and Senior Secondary
PHYSICS QUESTIONS
Coach : Mark

Question No. 1:
Two wheels roll side-by-side without sliding, at the same speed. The
radius of wheel 2 is twice the radius of wheel 1. The angular velocity of
wheel 2 is:
A. twice the angular velocity of wheel 1
B. the same as the angular velocity of wheel 1
C. half the angular velocity of wheel 1
D. more than twice the angular velocity of wheel 1
E. less than half the angular velocity of wheel 1

Question No. 2:
Two wheels are identical but wheel B is spinning with twice the angular
speed of wheel A. The ratio of the magnitude of the radial acceleration
of a point on the rim of B to the magnitude of the radial acceleration of
a point on the rim of A is:
A. 1
B. 2
C. 1/2
D. 4
E. 1/4

Question No. 3:
Three identical balls are tied by light strings to the same rod and rotate
around it, as shown below. Rank the balls according to their rotational
inertia, least to greatest.
A. 1, 2, 3
B. 3, 2, 1
C. 3, then 1 and 2 tie
D. 1, 3, 2
E. All are the same

Question No. 4:
Consider four objects, each having the same mass and the same radius:
1. a solid sphere
2. a hollow sphere
3. a flat disk in the x, y plane
4. a hoop in the x, y plane
The order of increasing rotational inertia about an axis through the
center of mass and parallel to the z axis is:
A. 1, 2, 3, 4
B. 4, 3, 2, 1
C. 1, 3, 2, 4
D. 4, 2, 3, 1
E. 3, 1, 2, 4

Question No. 5:
A particle might be placed
1. inside a uniform spherical shell of mass M, but not at the center
2. inside a uniform spherical shell of mass M, at the center
3. outside a uniform spherical shell of mass M, a distance r from the center
4. outside a uniform solid sphere of mass M, a distance 2r from the center
Rank these situations according to the magnitude of the gravitational force on
the particle, least to greatest.
A. All tie
B. 1, 2, 3, 4
C. 1 and 2 tie, then 3 and 4 tie
D. 1 and 2 tie, then 3, then 4
E. 1 and 2 tie, then 4, then 3

Question No. 6:
An object is dropped from an altitude of one Earth radius above
Earth’s surface. If M is the mass of Earth and R is its radius the speed
of the object just before it hits Earth is given by:
A. 𝑮𝑴/𝑹
B. GM/2R
C. 2GM/R
D. GM/R2
E. GM/2R2

Question No. 7:
A planet travels in an elliptical orbit about a star as shown. At what
pair of points is the speed of the planet the same?
A. W and S
B. P and T
C. P and R
D. Q and U
E. V and R

Question No. 8:
A source of frequency f sends waves of wavelength λ traveling with
speed v in some medium. If the frequency is changed from f to 2f, then
the new wavelength and new speed are (respectively):
A. 2λ, v
B. λ/2, v
C. λ, 2v
D. λ, v/2
E. λ/2, 2v

Question No. 9:
Two identical strings, A and B, have nearly the same tension. When
they both vibrate in their fundamental resonant modes, there is a beat
frequency of 3Hz. When string B is tightened slightly, to increase the
tension, the beat frequency becomes 6Hz. This means:
A. that before tightening A had a higher frequency than B, but after
tightening, B has a higher frequency than A
B. that before tightening B had a higher frequency than A, but after
tightening, A has a higher frequency than B
C. that before and after tightening A has a higher frequency than B
D. that before and after tightening B has a higher frequency than A
E. none of the above

Question No. 10:
The Doppler shift formula for the frequency detected is
f = f’
𝑣± 𝑣𝐷
𝑣 ± 𝑣𝑆
,
where f’ is the frequency emitted, v is the speed of sound, vD is the speed of
the detector, and vS is the speed of the source. Suppose the source is traveling
at 5m/s away from the detector, the detector is traveling at 7m/s toward the
source, and there is a 3-m/s wind blowing from the source toward the detector.
The values that should be substituted into the Doppler shift equation are:
A. vD = 7m/s and vS = 5m/s
B. vD = 10m/s and vS = 8m/s
C. vD = 4m/s and vS = 2m/s
D. vD = 10m/s and vS = 2m/s
E. vD = 4m/s and vS = 8m/s

Question No. 11:
The mass of an oxygen molecule is 16 times that of a
hydrogen molecule. At room temperature, the ratio of the
rms speed of an oxygen molecule to that of a hydrogen
molecule is:
A. 16
B. 4
C. 1
D. 1/4
E. 1/16

Question No. 12:
The temperatures TC of the cold reservoirs and the temperatures TH of the hot
reservoirs for four Carnot heat engines are
engine 1: TC = 400K and TH = 500K
Rank these engines according to their efficiencies, least to greatest.
A. 1, 2, 3, 4
B. 1 and 2 tie, then 3 and 4 tie
C. 2, 1, 3, 4
D. 1, 2, 4, 3
E. 2, 1, 4, 3

Question No. 13:
A ray of light passes through three media as shown. The speed of light in these
media obey:
a. v1 > v2 > v3
B. v3 > v2 > v1
C. v3 > v1 > v2
D. v2 > v1 > v3
E. v1 > v3 > v2

Question No. 14:
Let p denote the object-lens distance and i the image-lens distance. The image
produced by a lens of focal length f has a height that can be obtained from the
object height by multiplying it by:
A. p/i
B. i/p
C. f/p
D. f/i
E. i/f

Question No. 15:
Consider the following four statements concerning a compound microscope:
1. Each lens produces an image that is virtual and inverted.
2. The objective lens has a very short focal length.
3. The eyepiece is used as a simple magnifying glass.
4. The objective lens is convex and the eyepiece is concave.
Which two of the four statements are correct?
A. 1, 2
B. 1, 3
C. 1, 4
D. 2, 3
E. 2, 4

Question No. 16:
Two thin lenses (focal lengths f1 and f2) are in contact. Their equivalent focal
length F is:
A. f1 + f2
B. f1f2/(f1 + f2)
C. 1/f1 + 1/f2
D. f1 − f2
E. f1(f1 − f2)/f2

Question No. 17:
The light waves represented by the three rays shown in the diagram all
have the same frequency. 4.7 wavelengths fit into layer 1, 3.2
wavelengths fit into layer 2, and 5.3 wavelengths fit into layer 3. Rank
the layers according to the speeds of the waves, least to greatest.
A. 1, 2, 3
B. 2, 1, 3
C. 3, 2, 1
D. 3, 1, 2
E. 1, 3, 2

Question No. 18:
Consider the following energies:
1. minimum energy needed to excite a hydrogen atom
2. energy needed to ionize a hydrogen atom
3. energy released in 235U fission
4. energy needed to remove a neutron from a 12C nucleus
Rank them in order of increasing value.
A. 1, 2, 3, 4
B. 1, 3, 2, 4
C. 1, 2, 4, 3
D. 2, 1, 4, 3
E. 2, 4, 1, 3

Question No. 19:
Of the following, which has the smallest rest energy?
A. A neutron
B. An electron
C. An ion
D. A proton
E. An atom

Question No. 20:
Iron has atomic number 26. Naturally mined iron contains isotopes of
mass numbers 54, 56, 57, and 58. Which of the following statements is
FALSE?
A. Every atom of iron has 26 protons
B. Some iron atoms have 30 neutrons
C. Some iron atoms have 54 neutrons
D. The isotopes may be separated in a mass spectrometer
E. There are four kinds of naturally occurring iron atoms with the same
chemical properties

Question No. 21:
Bromine, with atomic mass 79.942 u, is composed of nearly equal
amounts of two isotopes, one of which contains 79 nucleons per atom.
The mass number of the other isotope is:
A. 78
B. 79
C. 80
D. 81
E. 82

Question No. 22:
The half-life of radium is about 1600 years. If a rock initially contains 1
g of radium, the amount left after 6400 years will be about:
A. 938 mg
B. 62 mg
C. 31 mg
D. 16 mg
E. less than 16 mg

Question No. 23:
The half-life of a radioactive isotope is 140 days. In how many days
does the decay rate of a sample of this isotope decrease to one-fourth
of its initial decay rate?
A. 35
B. 105
C. 187
D. 210
E. 280

Question No. 24:
65Cu can be turned into 66Cu, with no accompanying product except a
gamma, if bombarded with:
A. protons
B. neutrons
C. deuterons
D. electrons
E. alpha particles

Question No. 25:
An atom of 235U (Z = 92) disintegrates to 207Pb (Z = 82) with a half-life
of about a billion years by emitting seven alpha particles and β−
particles:
A. 3
B. 4
C. 5
D. 6
E. 7

Copy of HKISO FINAL ROUND Session 1 & 2 - S3 and SS.pdf

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