WAEC - Physics (2020)

1
In collision between two objects, kinetic energy is conserved only if
Απάντηση
(D)
the collision is elastic
2
The quantity of motion of a body is its
Απάντηση
(C)
mometum
3
The volume of a fixed mass of a gas varies inversely as the pressure on it provided the temperature is constant. This statement is
Απάντηση
(C)
Boyle's law
4
An image formed on a screen is always?
Απάντηση
(A)
inverted
5
How would the capacitance of a parallel plate capacitor be affected if the distance of separation of its plates is decreased? It will
Απάντηση
(A)
increase in value
6
Which of the following machines does not apply the lever principle?
Απάντηση
(C)
Single pulley
7
The average distance moved by a molecule between collisions is called
Απάντηση
(D)
mean free path
8
Which of the following waves requires a material medium for its propagation?
Απάντηση
(C)
Sound waves
9
The depolarising agent in a Leclanche cell is?
Απάντηση
(C)
manganese (IV) oxide
10
The material used to slow down the neutrons in a nuclear reactor is

Απάντηση
(C)
graphite
11
Which of the following statements explain why hot soapy water is more effective in cleaning oil-stained dishes?

Απάντηση
(B)
soap and heat decrease the surface tension of oil
12

The diagram above illustrates a beam of parallel rays from a distant object O, incident on one side of the total reflecting prism. Which diagram does not represent the correct path of the beam when it emerges from the prism?
Απάντηση
(A)
W
13
An electrical device has 50 turns in its primary coil and 20 turns in the secondary coil. The device can be a\an?

Απάντηση
(B)
step-down transformer
14
The earpiece of a telephone handset converts energy from
Απάντηση
(A)
electrical to sound
15
Two identical cups containing the same volume of water at 45°C and 5°C, are left in a room at 25°C. Which of the following graphs correctly illustrates the variation of temperature with time?

Απάντηση
(C)
C
16
A ray of light traveling from glass into ethyl alcohol is incident at the boundary at an angle of incidence 30\(^o\). Calculate the angle of refraction.

[Refractive index of glass =1.5; refractive index of ethyl alcohol = 1.36]

Απάντηση
(B)
33.5\(^o\)
17
A 60kg man stands on a weighing balance in an elevator. If the elevator accelerates upwards at 5ms\(^{-2}\), determine the reading of the scale. [g = 10ms\(^{-2}\)]

Απάντηση
(D)
900N
18
The length of an iron bar is 100cm at 20°C. At what temperature will its length increase by 0.01%? [Linear expansivity of iron = 1.2 x 10\(^{-5}\)°C]
Απάντηση
(C)
28.3°C
19
A moving-coil galvanometer which gives a full-scale on deflection with 0.005A is converted to a voltmeter reading up to 5V using an external resistance of 975\(\Omega\). What is the resistance of the metre?
Απάντηση
(C)
25.00\(\Omega\)
20
A beam consisting of \(\alpha\)-particles. \(\beta\)-particles and \(\gamma\)-rays pass through a magnetic field at right angles to the direction of the field. Which of the following observations would be made about the \(\alpha\)-particles, \(\beta\)-particles, and \(\gamma\)-rays respectively?
Απάντηση
(B)
Deflected, deflected, not deflected
21
A parallel plate capacitor is charged and the charging battery is subsequently disconnected. lf the plates of the capacitor are moved farther apart by means of insulating handles, the
Απάντηση
(B)
capacitance would decrease
22
The velocity of sound in air at 15°C is 340ms\(^{-1}\). Calculate the velocity at 47\(^o\)C
Απάντηση
(C)
358ms\(^{-1}\)
23

Which of the current-voltage characteristics shown above is that exhibited an ohmic conductor?

Απάντηση
(B)
B
24
A 500N box rests on a horizontal floor. A constant horizontal force is exerted on the box so that it moves through 8m. If the coefficient of kinetic friction between the floor and the box is 0.22, calculate the workdone on the box

Απάντηση
(A)
880J
25
The diagram illustrates a ball of mass m sliding down a plank inclined at an angle of 0 to the horizontal. The kinetic friction between the ball and the plank is F and acceleration of free fall is g. The normal force on the ball is?

Απάντηση
(C)
mgcos \(\theta\)
26

The diagram above illustrates a ball of mass m sliding down a plank inclined at an angle of 0 to the horizontal. The kinetic friction between the ball and the plank is F and the acceleration of free fall is g. The net force on the ball along the plank is?
Απάντηση
(C)
mgsin \(\theta\) - F
27
What factors determine the frequency of a note emitted by a vibrating string?
Απάντηση
(C)
Mass per unit length of string, tension in string and length of string
28
The magnitude of the force experienced by a charge of 1.6 x 10\(^{-8}\)C in a uniform electric field of intensity 5 x 10\(^5\)NC\(^{-1}\) is
Απάντηση
(C)
8.0 x 10\(^{-3}\)N
29
A motorcycle starting from rest is uniformly accelerated such that its velocity in 10s is 72kmhr\(^{-1}\). What is its acceleration?
Απάντηση
(D)
2ms\(^2\)
30
The temperature of an object is raised by 120°C. The resulting increase in its absolute temperature is

Απάντηση
(B)
120 K
31
Which of the following statements about the motion of a simple pendulum is true?
Απάντηση
(D)
lt swings faster at the poles than at the equator
32
An electron of mass m and charge e moves in a circular path in a magnetic field of flux density B. How long does it take to complete one orbit?
Απάντηση
(C)
\(\frac{2\pi m}{Be}\)
33
Which of the following statements about photoelectrons is correct?
Απάντηση
(B)
A red light releases a smaller number of electrons than a green light
34

The sketched graph above illustrates the heating curve of a 0.02kg of water. Determine the approximate value of the specific latent heat of vapourization of water

Απάντηση
(A)
2.25 x 10\(^6\) J kg\(^{-1}\)
35
In the hydraulic press, the force F applied is related to the diameter d of the cylinder by

Απάντηση
(A)
F \(\alpha\) d\(^2\)
36
In an electric circuit, an inductor of inductance 0.5 H and resistance 50\(\Omega\) is connected to an alternating current source of frequency 60 Hz. Calculate the impedance of the circuit.
Απάντηση
(C)
195.0 \(\Omega\)
37
Which of the following statements correctly explains why a total solar eclipse would be seen by people on only a small portion of the earth's surface? The

Απάντηση
(C)
earth revolves around the sun
38
Water waves have a wavelength of 3.6cm and speed of 18cms\(^{-1 }\) in deep water. If the waves enter shallow water with wavelength of 2.0cm, calculate the speed of the waves in the shallow water.
Απάντηση
(C)
10.0cms\(^{-1}\)
39
An a.c. generator can be converted to a d.c. electric motor by replacing the
Απάντηση
(A)
slip rings with a split ring and connecting a battery
40
A ray of light travels obliquely from a less dense medium to a denser medium. Which of the following statements is true about the light?

Απάντηση
(C)
The light refracts towards the normal
41
An electron of mass 9.1x 10\(^{-31}\) kg is travelling at a speed of 2.0 x 10\(^6\)ms\(^{-1}\). Calculate the associate wavelength of the electron. [h = 6.6. x 10\(^{-34}\) Js]
Απάντηση
(A)
3.63 x10\(^{-10}\) m
42
Which of the following statements about the process of melting of a solid are true? The temperature of the solid will

I. remain steady until melting starts.

ll. keep rising until melting starts,

Ill remain steady as melting proceeds.

V, keep rising as melting proceeds.
Απάντηση
(A)
I and llI only
43
A diver steps off a diving platform that is 10m above the water. If there is no air resistance during the fall, there will be a decrease in the diver's
Απάντηση
(A)
gravitational potential energy
44
Which of the following actions would increase the electric force between two positively charged particles?

Απάντηση
(B)
Decreasing the distance between the particles
45
A luminous object is one that
Απάντηση
(B)
gives out light of its own