2024 - JAMB Physics Past Questions and Answers - page 2

Here's the breakdown:

• The Key Concept: The color of an object is determined by the wavelengths of light it reflects. Objects absorb most wavelengths and reflect specific ones.
• Red Light and a Red Shirt: A red shirt reflects red light. When viewed under red light, the shirt still reflects red light, making it appear red. However, under white light, the shirt absorbs all other colors except red.
• Why the Answer is D: The red shirt under red light absorbs other colors and reflects red.

The question asks why water is unsuitable as a thermometric liquid. Let's analyze the statements:

• I. It wets glass: This is significant. If water wets the thermometer's glass, it clings to the sides, making temperature readings inaccurate due to meniscus changes.
• II. It needs to be coloured: Coloring water improves visibility but is not a fundamental reason for unsuitability. Other liquids can also be coloured.
• III. It has a low density: While true, it is not the primary reason. The main issue is wetting the glass.

Therefore, the most significant reason is that water wets glass.

Here's how to solve the problem:

1. Understand the forces: The tension in the rope has horizontal and vertical components. The horizontal component (effective force) is given as 15 N.
2. Use trigonometry: The angle to the vertical is 30º, so the angle to the horizontal is 60º. Horizontal component Fx = T x cos(θ), where T is tension and θ = 60º.
3. Solve for Tension (T): T = Fx / cos(60º) = 15 N / 0.5 = 30 N.

The mass of a substance deposited during electrolysis is directly proportional to its chemical equivalent. This is Faraday's second law of electrolysis. The chemical equivalent is defined as the atomic weight divided by the valency.

Here's how to solve the problem:

1. Calculate the volume of the cube: V = side³ = 1.5 cm x 1.5 cm x 1.5 cm = 3.375 cm³
2. Convert to m³: V = 3.375 x 10⁻⁶ m³
3. Calculate mass: m = ρ x V = 2700 kg/m³ x 3.375 x 10⁻⁶ m³ = 0.0091125 kg
4. Convert to grams: m = 0.0091125 kg x 1000 g/kg ≈ 9.1 g

The correct answer is Presbyopia. Here's why:

• Presbyopia: Condition where the lens loses flexibility with age, and ciliary muscles weaken, making it difficult to focus on near objects.
• Spherical aberration: Light rays passing through the lens are not focused at a single point.
• Astigmatism: Irregular cornea or lens shape causing blurred vision at all distances.
• Myopia: Nearsightedness; distant objects appear blurry as images focus in front of the retina.

Analysis of motion types:

• Translational motion: Movement in a straight line.
• Rotational motion: Spinning around an axis.
• Simple harmonic motion: Oscillatory motion.
• Circular motion: Movement along a circle.

Since the motion is linear from P to Q, the correct answer is translational motion.

Here's how to solve the problem:

1. Understand the concepts: Saturated Vapor Pressure (SVP) is the pressure when air is saturated. Dew point is the temperature at which air becomes saturated. Relative Humidity (RH) = (actual vapor pressure / SVP at current temperature) x 100%.
2. Given: SVP at 33ºC = 13.5 mmHg, SVP at 7ºC = 7.3 mmHg (actual vapor pressure at dew point).
3. Calculate RH: RH = (7.3 / 13.5) x 100 ≈ 54%

The frequency (f) of a sonometer is proportional to the square root of the tension (T): f ∝ √T. If tension increases four times (4T):

f' ∝ √(4T) = 2√T

Original frequency f = 50 Hz, so f' = 2 x 50 Hz = 100 Hz.

Air friction (air resistance) opposes motion through air.

• Streamlining: Shaping an object aerodynamically to reduce air resistance.
• Lubricating: Reduces friction between solid surfaces, not air friction.
• Propeller: Generates thrust, doesn't reduce friction.
• Polishing: Reduces surface roughness, not air friction.

Therefore, the friction due to air mass can be reduced by streamlining.