Which of the following are the correct SI units of the quantities indicated? i.N(Force) II. N/m (Torque) iii. watt(Power) iv. kgms-2(Momentum)
คำตอบ
(D)
i and iii only
2
A lorry travels 10km northwards, 4km eastwards, 6km southwards, 4km westwards to arrive at a point T. What is the total displacement?
คำตอบ
(B)
4km north
3
Two forces whose resultant is 100N, are at right angle to each other. If one of them makes an angle 30o with the resultant, determine its magnitude.
คำตอบ
(D)
86.6N
4
Which of the following quantities are scalars? i. Electrical potential ii. Torque iii. Momentum iv. Kinetic energy
คำตอบ
(D)
i and iv only
5
When taking a penalty kick, a footballer applies a force of 30.0N for a period of 0.05s. if the mass of the ball is 0.075kg, calculate the speed with which the ball moves off.
คำตอบ
(C)
20.00ms-1
6
A particle starts from rest and moves with a constant acceleration of 0.5ms-2. The distance covered by the particle in 10s is?
คำตอบ
(C)
25.0m
7
A 20-toothed gear wheel drives a 60-toothed one. If the angular speed of the smaller wheel is 120 rev s-1, the angular speed of the larger wheel is
คำตอบ
(C)
360 rev s-1
8
How long will it take a 60kg man to climb a height of 22m if he expended energy at a rate of 0.25kW. [g = ms-2]
คำตอบ
(D)
52.8s
9
A force, 10N, drags a mass 10kg on a horizontal table with an acceleration of 0.2ms. If the acceleration due to gravity is 10ms-1, the coefficient of friction between the moving mass and the table is
คำตอบ
(B)
0.08
10
A body whose mass is 2kg and has a volume of 500cm3 just floats when completely immersed in a liquid. Calculate the density of the liquid
คำตอบ
(B)
4.0 x 103kgm-3
11
The product PV where P is pressure and V is volume has the same unit as
คำตอบ
(C)
energy
12
The amount of heat needed to raise the temperature of 10kg of copper by 1k is its
คำตอบ
(B)
heat capacity
13
A tap supplies water at 25oC while another supplies water at 75oC. If a man wishes to bathe with water at 40oC, the ratio of the mass of cold water to the mass of hot water required is
คำตอบ
(C)
7 : 3
14
When heat is applied to one end of a metal rod, the molecules at the other end soon begin to vibrate with greater amplitude than before because heat has been transferred by
คำตอบ
(C)
conduction
15
Which of the following media allow the transmission of sound wave through them i. Air. ii. Liquids. iii. Solids.
คำตอบ
(D)
i,ii and iii
16
Which of the following properties is/are common to all waves? i. Diffraction ii. Refraction iii. Interference
คำตอบ
(D)
i, ii, and iii
17
A piano wire 0.5m long has a total mass of 0.01kg and is stretched with a tension of 800N. Calculate the frequency of the wire when it sounds its fundamental note
คำตอบ
(A)
200Hz
18
A note is called an octave of another note when
คำตอบ
(A)
its frequency is twice that of the first note
19
Which of the following factors affects the speed of sound in air? i. Temperature ii. pressure iii. Frequency
คำตอบ
(A)
i only
20
The speed of sound in air at sea level is 340ms\(^{-1}\) while that of light is 300 000kms\(^{-1}\). How far (to the nearest meter) from the center of a thunderstorm is an observer who hears a thunder 2s after a lightning flash?
คำตอบ
(D)
680m
21
A slight loading of a tuning fork has the effect of
คำตอบ
(C)
decreasing its frequency
22
Two strings of the same length and under the same tension gives notes of frequencies in the ratio 4 : 1. The masses of the strings are in the corresponding ratio of
คำตอบ
(D)
1 : 16
23
To obtain a magnification of 2.5, how far should an object be placed from the pole of a thin converging lens of focal length 10.20m?
คำตอบ
(C)
0.28m
24
An object is placed 10cm in front of a concave mirror of focal length 15cm. What is the position and nature of the image formed?
คำตอบ
(A)
30cm and virtual
25
Which of the following phenomena explains the formation of a mirage? i. Reflection ii. Refraction iii. Diffraction
คำตอบ
(A)
i and ii only
26
When white light is dispersed by a spectrometer, the component having the shortest wavelength is
คำตอบ
(C)
violet
27
Which of the following statement is TRUE of ultraviolet, visible and infra-red rays?
คำตอบ
(B)
ultra-violet rays have shorter wavelengths than infra-red rays and produce flourescence
28
A spectrum of sunlight is said to be impure when
คำตอบ
(C)
the different colours in it overlap
29
A cell of internal resistance 2 ohms supplies current to a 6 ohms resistor. The efficiency of the cell is
คำตอบ
(D)
75.0%
30
When a resistance R is across a cell, the voltage across the terminals of the cell is reduced to two-third of its normal value. The internal resistance of the cell is
คำตอบ
(B)
\(\frac{1}{2}\)R
31
A household refrigerator is rated 200 watts. If electricity costs 5k per kWh, what is the cost of operating it in 20 days?
คำตอบ
(A)
N4.80
32
Which of the following ammeters may be used to measure alternating currents? i. moving-coil ammeter ii. moving-iron ammeter iii. hot-wire ammeter
คำตอบ
(B)
ii and iii only
33
The principle of operation of an induction coil is based on
คำตอบ
(C)
Faraday's law
34
A dynamo primarily combines
คำตอบ
(A)
mechanical energy into electrical energy
35
In a certain fusion reaction, a deuteron (\(^{2}_{1}H\)) interacts with a triton (\(^{3}_{1}He\)) and produces an a-particle (\(^{4}_{2}He\)) and a second product. The second product is
คำตอบ
(C)
a neutron
36
Which of the following symbolic representations is correct for an atom X with 22 electrons and 43 neutrons?
คำตอบ
(D)
\(^{65}_{22}X\)
37
the fig above shows displacement-time graphs for three different motions. which of the following statements is correct?
คำตอบ
(B)
graph 1 corresponds to zero velocity
38
the fig above shows three different ways of hanging a heavy picture from a hook. the tension in the string will be?
คำตอบ
(B)
Greatest in Y
39
When one arm of a U-tube manometer is connected to a gas supply, the levels of mercury in the two arms of the U-tube is shown in the figure above, if the atmospheric pressure is 76.0cm hg, the gas pressure is
คำตอบ
(D)
85.9cm hg
40
The fig above shows two waveforms X and Y. If the frequency of X is 30Hz what is the frequency of Y
