2021 - JAMB Physics Past Questions and Answers - page 4
The temperature gradient across a copper rod of thickness 0.02m, maintained at two temperature junctions of 20º and 80ºC respectively is?
3.0 x 10\(^{2}\)km\(^{-1}\)
3.0 x 10\(^{3}\)km\(^{-1}\)
5.0 x 10\(^{3}\)km\(^{-1}\)
3.0 x 10\(^{4}\)km\(^{-1}\)
\(\Delta\) = \(\frac{\bigtriangleup\theta}{\delta}
= \frac{80-20}{0.02}\)
= 3.0 x 10\(^{3}\)km\(^{-1}\)
Calculate the mass of ice that would melt when 2kg of copper is quickly transferred from boiling water to a block of ice without heat loss (specific heat capacity of copper = 400Jkg\(^{1}\)k\(^{-1}\), latent heat of fusion of ice = 3.3 x 10\(^{5}\)Jkg\(^{-1}\))
\(\frac{8}{33}\)kg
\(\frac{3.3}{80}\)kg
\(\frac{80}{33}\)kg
\(\frac{3.3}{8}\)kg
mc\(\Delta\theta\) = m\(\lambda\)f
2 x 400 (100 - 0) = m(3.3 x 10\(^{5}\))
m = \(\frac{2 \times 400 \times 100}{3.3 \times 10^{5}}
= \frac{8}{33}\)kg
The equation of a wave traveling along the positive x-direction is given by; y = 0.25 x 10\(^{-3}\) sin (500t - 0.025x). Determine the angular velocity of the wave motion.
0.25 x 10\(^{-3}\)rads\(^{-1}\)
0.25 x 10\(^{-1}\)rads\(^{-1}\)
5.00 x 10\(^{2}\)rads\(^{-1}\)
2.50 x 10\(^{3}\)rads\(^{-1}\)
y = A sin (wt + 0)
y = 0.25 x 10\(^{-3}\)sin (500t - 0.025x)
w = 5.00 x 10\(^{2}\)rads\(^{-1}\)
If a sound wave goes from a cold air region to a hot air region, its wavelength will...?
increase
decrease
decrease then increase
remain constant
When sound travels from hot air to cold air or from cold air to hot air it will refract, the molecules of air are moving faster and the vibrations of the sound wave can therefore be transmitted faster. Hence, the speed of sound is greater in hot air than it is in cold air
The lowest note emitted by a stretched string has a frequency of 40Hz. How many overtones are there between 40Hz and 180Hz?
4
3
2
1
f\(_{0}\) = 40H\(_{3}\)
1st overtone = 2f\(_{0}\) = 80H\(_{3}\)
2nd overtone = 3f\(_{0}\) = 120H\(_{3}\)
3rd overtone = 4f\(_{0}\) = 160H\(_{3}\)
4th overtone = 5f\(_{0}\) = 200H\(_{3}\)
Hence, the number of overtones between 40H\(_{3}\) and 180H\(_{3}\) = 3
A man stands 4m in front of a plane mirror. If the mirror is moved 1m towards the man, the distance between him and his new image is?
3m
5m
6m
10m
object distance (u) = image distance (v)
u = 3m
u|v| = 3 + 3 = 6m
The inside portion of part of a hollow metal sphere of diameter 20cm is polished. The portion will therefore form a?
concave mirror of focal length 5cm
concave mirror of focal length 10cm
convex mirror of focal length 5cm
convex mirror of focal length 10cm
f = \(\frac{m}{4}\)
= \(\frac{d}{4}\)
= \(\frac{20}{4}\)
= 5cm
The velocities of light in air and glass are 3.0 x 10\(^8\)ms\(^{-1}\) and 2.0 x 10\(^8\)ms\(^{-1}\) respectively. If the angle of refraction is 30º, the sine of the angle of incidence is?
0.33
0.50
0.67
0.75
\(\frac{\text {sin i}}{\text {sin r}}\) = \(\frac{\text {velocity in air}}{\text {velocity in glass}}\)
\(\frac{\text {sin i}}{\text {sin 30}}\) = \(\frac{3 \times 10^{8}}{2 \times 10^{8}}\)
sin i = \(\frac{3}{4}\)
= 0.75
An astronomical telescope is said to be in normal adjustment when the?
A 2H inductor has negligible resistance and is connected to a \(\frac{50}{\pi}\) Hz A.C supply. The reactance of the inductor is?