2003 - JAMB Physics Past Questions and Answers - page 2
The table above shows the saturation vapour pressure against temperature in a certain town. If the vapour pressure in this town at 20oC is 10mmHg, what is the relative humidity?
R.H = Partial Pressure of Water Vapour Presentx100_1S.V.P at temperature of atmosphere
= _10x100_117.50
= 57.14%
Users' Answers & Comments[speed of sound in air = 340ms-1]
In vibration in a closed pipe/tube, the first resonance occurs at a position L = V/4f,
when reading from the top of the tube,
| L1 = | _340 |
| 4 x 340 |
= 0.25m
L2 = 3V/4f
| L2 = | 3 x 340 |
| 4 x 340 |
= 0.75m
L3 = 5V/4f
| L3 = | 5 x 340 |
| 4 x 340 |
= 1.25m
However, the effective length of the tube is 1.2m. Thus reading from below, the first position of resonance will be 1.20 - 0.75m = 0.45m
Users' Answers & CommentsForm the lens formula = 1/U + 1/V = 1/f
=> 1/10 + 1/25 = 1/f;
∴ (5 + 2) / 50 = 1/f
∴ f = 50/7cm
since the image is observed on a screen, it is a real image. Thus magnification
M = f/U-f
| = | __50/7 |
| 10 - 50/7 |
| ∴ M = | 50/7 |
| 20/7 |
= 50/7 x 7/20 = 2.5
Users' Answers & CommentsTwo thermal objects are said to be in a thermal equilibrium when the temperature of both objects are equal. Generally, heat flows from an object at a higher temperature to the one at a lower temperature until both temperature are the same, during which the two bodies are said to be in thermal equilibrium
Users' Answers & CommentsIn vibration in a closed pipe/tube as shown in the figure, fundamental note is produced at the first position of resonance. When the length of the air column L = λ/4; => λ = 4L. Since the open end of the tube is taken as an antinode; and closed end as the node.
Thus the associated frequency is given by
f = V/λ = V/4L
∴ f = V/4L
Users' Answers & Comments[coefficient of linear expansion of steel = 11 x 10-6K-1]
The increase in length of the steel rail is given by
= α 10
= 11 x 10-6 x 20 x (40 -20)
= 11 x 10-6 x 20 x 20
= 4.4 x 10-3
∴ Final length will be original length plus increase in length
= 20 + 4.4 x 10-3
= 20 + 0.0044
= 20.0044m
Users' Answers & CommentsFor a concave mirror to produce an image at infinity, the image has to be place at the principal focus of the mirror
Users' Answers & CommentsIn general intensity of a wave is the rate of flow of energy across unit area normal to the direction of propagation of the wave intensity α1/r2 where r is the distance away from the point source. Thus if the distance from the point source of the sound wave is doubled, then the intensity will be decreased by a factor of 4
Users' Answers & Comments