1997 - JAMB Physics Past Questions and Answers - page 3
21
A mass of a liquid at 30oC is mixed with a mass of the same liquid at 70oC and the temperature of the mixture is 45oC. Find the ratio of the mass of the cold liquid to the mass of the other liquid.
A
3 : 5
B
5 : 3
C
3 : 7
D
7 : 3
correct option: b
Heat lost = heat gained
mH x c x (70 - 45) = mc x c x (45 - 30)
\(\frac{m_c}{m_H}\) = \(\frac{5}{3}\)
Users' Answers & CommentsmH x c x (70 - 45) = mc x c x (45 - 30)
\(\frac{m_c}{m_H}\) = \(\frac{5}{3}\)
22
What happens when a gas expands at constant temperature?
A
its pressure decreases
B
the total momentum of its molecules remains constant
C
its pressure decreases and the total momentum of its moleculees remains constant
D
its pressure decreses and the total kinetic energy of its molecule decreases
correct option: a
Users' Answers & Comments23
Ripples on water and light waves are similar because both
A
have the same frequency
B
can be refracted and diffracted
C
are longitudinal waves
D
have the same velocity
correct option: c
Users' Answers & Comments24
Under constant tension and constant mass per unit length, the note produced by a plucked string is 500Hz when the length of the string is 0.90m. At what length is the frequency 150Hz?
A
3m
B
4m
C
5m
D
6m
correct option: a
F = \(\frac{1}{2L}\)\(\sqrt\frac{T}{m}\)
F1L1 = F2L2
500 x 0.9 = 150 x L2
therefore, L2 = 3m
Users' Answers & CommentsF1L1 = F2L2
500 x 0.9 = 150 x L2
therefore, L2 = 3m
25
The colours seen in the thin films of oil on the road and in soap bubbles are due to
A
reflection
B
interference
C
diffraction
D
polarization
correct option: a
Users' Answers & Comments26
If the load at the end of a sonometer wire is immersed in a bucket of water, the original fundamental frequency of the wire could be restored by
A
decrease the length of the wire
B
increasing the length of the wire
C
increasing the mass per unit length of the wire
D
changing the temperature of the wire
correct option: b
Users' Answers & Comments27
A boy on looking into a mirror observed that his face appeared to have grown bigger. The boy must have been looking at a
A
convex mirror with his face at the focus
B
concave mirror with his face between the focus and the mirror
C
concave mirror with his face at the focus
D
convex mirror with his face between the focus and the mirror
correct option: b
Users' Answers & Comments28
Light of velocity 3 x 108ms-1 is incident on a material of reflective of index n. If the velocity of light is reduced to 2.4 x 108ms-1 in the material, what is n?
A
2.33
B
2.25
C
1.33
D
1.25
29
The electromagnetic waves that are sensitive to temperature changes are
A
X-rays
B
Gamma-rays
C
Ultra-violet rays
D
Infra-red rays
correct option: d
Users' Answers & Comments30
Three electric cells each of e.m.f 1.5V and internal resistance of 1.0\(\Omega\) are connected in parallel across an external resistance of \(\frac{2}{3}\)\(\Omega\). Calculate the value of the current in the resistor
A
0.5 A
B
0.9A
C
1.5A
D
4.5A
correct option: c
E.m.f = 1.5
r = \(\frac{1 \times\ 1 \times 1}{(1 \times\ 1) + (1 \times\ 1) + (1 \times\ 1)}\)
r = \(\frac{1}{3}\)\(\Omega\)
I = \(\frac{E.m.f}{r + R}\)
I = \(\frac{1.5}{\frac{1}{3}\ + \frac{2}{3}}\)
I = 1.5A
Users' Answers & Commentsr = \(\frac{1 \times\ 1 \times 1}{(1 \times\ 1) + (1 \times\ 1) + (1 \times\ 1)}\)
r = \(\frac{1}{3}\)\(\Omega\)
I = \(\frac{E.m.f}{r + R}\)
I = \(\frac{1.5}{\frac{1}{3}\ + \frac{2}{3}}\)
I = 1.5A