Physics Past Questions | West African Examinations Council (WAEC)

Question 41

A wire, 20m long is heated from a temperature of 5°C to 55°C. If the change in length is 0.020m, calculate the linear expansivity of the wire

Options

A) 1.0 × 10^-3k^-1

B) 2.0 × 10^-4k^-1

C) 2.0 × 10^-5k^-1

D) 1.0 × 10^-5k^-1

E) 2.0 × 10^-6k^-1

The correct answer is B.

Explanation:

$\alpha =\frac{\Delta L}{L\Delta \theta }=\frac{0.020}{20\times (55-5)}=2.0\times {10}^{-4}$

Question 42

in temperature of the water between the top and bottom of the water fall. Neglect heat loses(g = 10.0m^-2 specific heat capacity of water = 4.20 × 10^-3 JKg^-1 K^-1)

Options

A) 0.1°C

B) 1.0°C

C) 42°C

D) 100°C

E) 4.20°C

The correct answer is B.

Explanation:

Potential Energy = Heat Energy
mgh = Mc$\Delta \theta =\frac{gh}{c}=\frac{10\times 240}{4.20\times {10}^3}$

= 1.0°C

Question 43

The set-up illustrated above shows a capillary tube of uniform cross-sectional area in two different arrangements. Using the data in the diagrams. Calculate the pressure of the atmosphere

Options

A) 76cm of Hg

B) 75cm of Hg

C) 74cm of Hg

D) 60cm of Hg

E) 45cm of Hg

The correct answer is B.

Explanation:

The set-up illustrated above shows a capillary tube of uniform cross-sectional area in two different arrangements. Using the data in the diagrams. Calculate the pressure of the atmosphere

P₁ = p + 15, p₂ = p - 15
v₁ = 30cm, v₂ = 45cm
P₁v₁ = p₂v₂
p = 75cm of Hg

Question 44

A fixed mass of gas of volume 600cm³ at a temperature of 27°C is cooled at constant pressure to a temperature of 0°C. What is the change in volume?

Options

A) 54cm²

B) 273cm²

C) 300cm²

D) 546cm²

E) 600cm²

The correct answer is A.

Explanation:

$\frac{V_1}{T_1}=\frac{V_2}{T_2}$

T₂ = 0 + 273 = 273k
V₁ = 600
T₁ = 27 + 273 = 300k
V₂ = $\frac{V_1{T}_2}{T_1}$

= 546cm
V₁ - V₂ = 54cm

Question 45

The boiling point of a liquid depends on the following except the

Options

A) nature of the liquid

B) external pressure

C) volume of the liquid

D) impurities present in the liquid

E) degree of it's molecular cohesive force

The correct answer is C.

Question 46

A team trap is a component of the apparatus used in determining the specific latent heat of vaporisation of steam. In the steady steady state, the steam trap

Options

A) stores the steam for future use

B) prevents the steam from escaping

C) ensures that only dry steam gets into the calorimeter

D) allows condensed steam to go into the calorimeter

E) determine the quantity of steam used

The correct answer is C.

Question 47

A tap supplies water at 26°C while another supplies water at 82°C. If a man wishes to bathe with water at 40°C the ratio of hot mass of hot water to that of cold water required is

Options

A) 1:3

B) 3:1

C) 3:7

D) 7:3

E) 15:8

The correct answer is A.

Explanation:

Heat supplied by hot water = heat gained by cold water M₁C(82 - 40) = M₂C(40 - 26)
$\frac{M_2}{M_1}$

= $\frac{14}{42}$

= 1:3

Question 48

Melting ice cools an orange drink far better than the same mass of ice-cold water because

Options

A) melting ice is lower temperature than ice-cold water

B) water has a higher specific heat than ice

C) ice floats and cools the air above the drink

D) ice absorbs latent heat during melting

E) ice makes better thermal contact than water

The correct answer is D.

Question 49

The saturation vapour of a liquid depends on its

Options

A) volume

B) temperature

C) mass

D) density

E) pressure

The correct answer is B.

Question 50

Two forces, whose resultant is 100N are perpendicular to each other. If one of them makes an angle of 60° with the resultant, calculate the magnitude. (Sin 60° = 0.8660, Cos 60° = 0.500)

Options

A) 200.0N

B) 173.2N

C) 115.5N

D) 86.6N

E) 50.0N

The correct answer is E.

Explanation:

x = 100 cos50° = 50N

Question 51

The graph above shows the expansion of water as the temperature increases from 0°C. Which of the following deductions from the graph are true?
i. Water has its maximum density at Q.
ii. The volume of water is greater at 0°C than at 4°C.
iii. The volume of water decreases uniformly when cooled from 100°C. iv. When water solidifies, its volume increases

Options

A) i and ii only

B) i and iii only

C) ii and iii only

D) i, ii and iii only

E) i, ii and iv only

The correct answer is E.

Question 52

Two mirrors are inclined as shown in the diagram. A ray of light RO strikes the arrangement at O and emerges along PO. The emergent ray has been deviated through

Options

A) 240×

B) 180×

C) 120×

D) 60×

E) 30×

The correct answer is B.

Question 53

In the arrangement illustrated above, Y and B are yellow and blue transparent light filters respectively through the filters is

Options

A) blue

B) red

C) yellow

D) green

E) black

The correct answer is E.

Question 54

A ray of light is incident at an angle of 30° on a glass prism of refractive index 1.5. Calculate the angle through which the ray is minimally deviated in the prism. (The medium surrounding the prism is air)

Options

A) 10.5°

B) 19.5°

C) 21.1°

D) 38.9°

E) 40.5°

The correct answer is A.

Explanation:

n = sinisinr
sin r = 30∘n
sin r = 0.51.5
sin r = 0.3333
r = 19.5°; Deviation 30 - 19.5 = 10.5°

Question 55

Calculate the refractive index of the material of the glass block shown in the diagram if YZ = 4cm

Options

A) 0.40

B) 0.60

C) 1.50

D) 1.67

E) 2.50

The correct answer is D.

Explanation:

Calculate the refractive index of the material of the glass block shown in the diagram if YZ = 4cm

n = real depthapparent depth
1010−4 = 1.6

Question 56

An image which can be formed on a screen is said to be

Options

A) virtual

B) blurred

C) inverted

D) erect

E) real

The correct answer is E.

Question 57

Which of the following are true of plane-polarised right?
i. Plane polarisation of light is the formation of hydrogen bubbles on the particle of light.
ii. Plane components.
iii. A plane polarised light vibrates in one plane.
iv. Polarisation of light is characteristic of transverse vibration

Options

A) i and ii only

B) i and iv only

C) ii and iii only

D) i and ii only

The correct answer is D.

Question 58

At which of the following distances from the lens should a slide be placed on a slide projector if f is the focal length of the projector length?

Options

A) less than f

B) greater than f but less than 3f

C) equal to f

D) equal to 2f

E) greater than 2f

The correct answer is C.

Question 59

What part of the camera corresponds to the iris of the eye?

Options

A) shutter

B) film

C) lens

D) diaphram

E) focusing ring

The correct answer is D.

Explanation:

The diaphragm is placed in the light path of a lens or objective, and the size of the aperture regulates the amount of light that passes through the lens. The centre of the diaphragm's aperture coincides with the optical axis of the lens system.

A natural optical system that has a diaphragm and an aperture is the human eye. The iris is the diaphragm, and the opening in the iris of the eye (the pupil) is the aperture. An analogous dev in a photographic lens is called an iris diaphragm.

Question 60

Which of the following is not a mechanical wave?

Options

A) wave propagatd in stretched string

B) wave in closed pipe

C) radio waves

D) water waves

E) sound waves

The correct answer is C.

Explanation:

A mechanical wave is a wave that is an oscillation of matter, and therefore transfers energy through a medium. While waves can move over long distances, the movement of the medium of transmission—the material—is limited. Therefore, the oscillating material does not move far from its initial equilibrium position. All of the options are mechanical waves except radio wave which is an electromagnetic wave of a frequency between about 10⁴ and 10¹¹ or 10¹² Hz, as used for long-distance communication.

LOADING MORE.............