Which of the following phenomena causes capillary of liquids in tubes of narrow bore?
คำตอบ
(B)
surface tension
2
Which of the following physical quantities are derived? i. Area ii. Thrust iii. Pressure iv. Mass
คำตอบ
(B)
i, ii and iii only
3
A block of volume 3 x 105m3 and density 2.5 x 103 kg m-3 is suspended from a spring balance with \(\frac{2}{3}\) of its volume immersed in a liquid of density 900 kg m-3. Determine the reading of the spring balance [g = 10ms-2]
คำตอบ
(B)
0.57N
4
A solid body will float in a liquid if its
คำตอบ
(A)
density is less than that of a liquid
5
An object is said to undergo oscillatory motion when it moves
คำตอบ
(B)
to and fro about a fixed point
6
A body is rotating in a horizontal circle of radius 2.5m with an angular speed of 5 rad s-1. Calculate the magnitude of the radial acceleration of the body
คำตอบ
(C)
12.50ms-2
7
A moving car of mass 800 kg experiences a frictional force of 200N. If it accelerates 2 ms-2, calculate the magnitude of the force applied to the car
คำตอบ
(D)
1800N
8
Uniform speed occurs when there is equal change of
คำตอบ
(A)
distance in equal times
9
A car accelerates uniformly from rest at 5 ms-2. Determine its speed after 10s
คำตอบ
(A)
50.0ms-1
10
Which of the following quantities is a vector?
คำตอบ
(D)
momentum
11
which of the following statements about simple harmonic motion is correct? The
คำตอบ
(A)
total mechanical energy is always conserved
12
A force acting on a body causes a change in the momentum of a body from 12 kg ms-1 to 16kg ms-1 in 0.25. Calculate the magnitude of the impulse
คำตอบ
(C)
4.0Ns
13
Which of the following source of energy is renewable?
คำตอบ
(C)
hydro
14
A stone of mass 2.0kg is thrown vertically upward with a velocity of 20.0 ms-1, calculate the initial kinetic energy of the stone
คำตอบ
(B)
400J
15
Which of the following statements about the mouth piece of a telephone is correct? It converts sound energy into
คำตอบ
(C)
electrical energy
16
The potential energy in an elastic string of force constant K which has been extended by X metres is expresses as
คำตอบ
(A)
\(\frac{1}{2}k \Box ^2\)
17
The engine of a train produces a force of 3000N when moving at 30.ms-1. calculate the power of the engine
คำตอบ
(C)
9.00 x 104W
18
The velocity ratio of an inclined plane, inclines at an angle \(\theta\) to the horizontal can be expressed as
คำตอบ
(A)
(sin \(\theta)^{-1}\)
19
A block and tackle system has six pulleys. a force of 50N applied to it lifts a load of weight W. If the efficiency of the system is 40%, calculate W
คำตอบ
(D)
120N
20
The sagging of overhead electrical cables is the consequence of
คำตอบ
(A)
linear expansivity
21
The silvered surface in a vacuum flask reduces heat loos due to
คำตอบ
(C)
radiation
22
How long will it take to heat 3kg of water from 28oC to 88oC in an electric kettle taking 6a from a 220V supply? [specific heat capacity of water = 4180 J kg-1K-1]
คำตอบ
(B)
570s
23
The amount of energy required to change a kilogram of ice in water without a change in temperature is
คำตอบ
(D)
specific latent heat of fusion of ice
24
A quantity of steam at 100oC condenses to water at the same temperature by releasing 6.9 x 104J of energy. Calculate the mass of the condensed steam. [specific latent heat of vaporization of eater = 2.3 x 106 J kg-1]
คำตอบ
(B)
3.0 x 10-2 kg
25
The temperature of a liquid falls after some of it has evaporated because
คำตอบ
(B)
the more energetic molecules have escaped into the atmosphere
26
The S.I units of frequency, period and amplitude of a wave are respectively
คำตอบ
(D)
hertz, second and metre
27
a note of frequency 2000Hz has a velocity of 400 ms-1. calculate the wavelength of the note
คำตอบ
(D)
0.2m
28
The eclipse of the moon occurs when the
คำตอบ
(B)
earth comes exactly between the moon and the sun
29
Which of the following observations cannot be explained using the rectilinear propagation of light?
คำตอบ
(D)
diffraction patterns of light
30
The distance between the successive crests of a wave travelling at 20ms\(^{-1}\) is 25cm. Calculate the frequency of the wave
คำตอบ
(D)
80.0hz
31
A ray from a fixed object is incident on a plane mirror at an angle of 20o. If the mirror is rotated through 30o by how many degree would the reflected ray rotate?
คำตอบ
(A)
60o
32
Which of the following distances is usually adjustable in the camera? The distance between the
คำตอบ
(A)
lens and the film
33
A travelling microscope is focused on a mark on a table. If a glass block of thickness 18.0cm is placed on the mark by how many centimeters will the microscope be moved upwards so as to focus the mark once again? [refractive index of glass = 1.5]
คำตอบ
(D)
6cm
34
In which of the following media would sound wave travel fastest?
คำตอบ
(C)
iron
35
Which of the following actions is necessary in order to tune a string to produce a note of an octave higher than its fundamental?
คำตอบ
(B)
reducing the tension by half
36
The acceleration due o gravity may be defined as the force
คำตอบ
(C)
with which the earth attracts one kilo-gram mass
37
An electron of mass m and charge \(\Box\) enters a uniform electric field between two metal plates P and q separated by a distance d. P is maintained at a potential V while Q is earthed. Determine an expression for the magnitude of the acceleration of electron through the field
คำตอบ
(A)
\(\frac{eV}{md}\)
38
Which of the following factors does not affect the capacitance of a parallel plate capacitor?
คำตอบ
(B)
nature of the surface of the plates
39
The equivalent capacitance of a 3\(\mu F\) capacitor and a 6\(\mu F\) capacitor connected in parallel is
คำตอบ
(D)
9.0\(\mu F\)
40
a cell of e.m.f. 1.5V and internal resistance 1.0\(\Omega\) is connected to two resistor of resistance 2.0\(\Omega\) and 3.0\(\Omega\) in series. Calculate the current through the resistors
คำตอบ
(A)
0.25A
41
An electric lamp rated 120W is used on a 240Vrms, calculate the resistance of its filament
คำตอบ
(A)
480\(\Omega\)
42
Which of the following statements about a bar magnet is correct?
คำตอบ
(D)
the magnetic properties are more pronounced at points near the end of the bar
43
The force experienced by a current-carrying conductor move in a magnetic field is employed in the working of the i. moving coil ammeter ii. electric bell iii. electric motor. Which of the statements above are correct?
คำตอบ
(C)
i and iii only
44
The breaking up of an atomic nucleus into the fragment of nearly equal size is known as
คำตอบ
(B)
nuclear fission
45
A 500kV is applied across an X-ray tube. Calculate the maximum velocity of the electrons produced [Me = 9.1 x 10-31kg, e = 1.6 x 10-19C]
