2014 - WAEC Physics Past Questions and Answers - page 3
21
A quantity of water at 20oC is mixed with another quantity of water at 70oC. The final steady temperature of the mixture is 40oC. Determine the ratio of the mass of the cold water to that of the hot water
A
7:2
B
3:2
C
2:5
D
1:2
correct option: b
Q = MC\(\theta\)
M = \(\frac{Q}{C\theta}\)
\(\frac{Q}{20C}\) : \(\frac{Q}{30C}\)
= 3:2
Users' Answers & CommentsM = \(\frac{Q}{C\theta}\)
\(\frac{Q}{20C}\) : \(\frac{Q}{30C}\)
= 3:2
22
The mass of an empty density bottle is 30g. When filled with a liquid, the mass reduces to 38g. Calculate the apparent cubic expansivity of the liquid
A
6.25 x 10K-1
B
6.25 x 10-3K-1
C
2.50 x 10-3K-1
D
2.50 x 10-4K-1
correct option: b
Apparent cubic expansivity = \(\frac{\text{mass of hot liquid expelled}}{\text{mass of hot liquid left x temp. rise}}\)
= \(\frac{2}{8 \times 40} = 0.00625\)
Users' Answers & Comments= \(\frac{2}{8 \times 40} = 0.00625\)
23
a ca travelling at 30m-1 overcomes a frictional resistance of 100N while moving. Calculate the power developed by the engine. [1 hp = 0.75 kW]
A
0.23hp
B
0.40hp
C
4.00hp
D
4.40hp
correct option: c
P = FV = \(\frac{100 \times 30}{1000} = 3 kW\)
\(\frac{3}{0.75} = 4hp\)
Users' Answers & Comments\(\frac{3}{0.75} = 4hp\)
24
The quality of a note depends on its
A
frequency
B
pitch
C
overtones
D
amplitude
correct option: c
Users' Answers & Comments25
A transverse wave can be distinguished from a longitudinal wave by
A
diffraction
B
relection
C
refraction
D
polarization
correct option: d
Users' Answers & Comments26
Refraction of lights differs from reflection in that, in refraction i. at least two media are involved ii. there is a change in the direction of the ray iii. the speed of the ray changes. Which of the statements above is/are correct?
A
i only
B
i ad ii only
C
ii and iii only
D
i and iii only
correct option: b
Users' Answers & Comments27
Which of the following relations about the focal length fo of the objective and focal length fe of the eye piece of a compound is correct?
A
fo = fe
B
fo < fe
C
fo > fe
D
fe = 2fo
correct option: b
Users' Answers & Comments28
The functional difference between a lens and a mirror is that a lens
A
reflects a beam of light while a mirror refracts it
B
refracts a beam of light while a mirror reflects it
C
absorbs incident rays while a mirror transmit them
D
transmits incidents ray whle a mirror absorbs them
correct option: b
Users' Answers & Comments29
The diagram above illustrates an electromagnetic wave travelling with speed 3.0 x 108ms-1. Calculate the wave length of the wave
A
0.05m
B
0.15m
C
0.16m
D
0.40m
correct option: c
Users' Answers & Comments30
A fish inside a pond appears to be at a depth of 1.5m when viewed vertically from above. The refractive index of the water in the pound is 1.3. Calculate the apparent displacement of the fish
A
2.50m
B
1.95m
C
1.50m
D
0.45m
correct option: d
Real depth = n x apparent depth
= 1.3 x 1.5 = 1.95m
Apparent displacement = 1.95 - 1.5 = 0.45m
Users' Answers & Comments= 1.3 x 1.5 = 1.95m
Apparent displacement = 1.95 - 1.5 = 0.45m